All thinkpads have a Wifi card whitelist at the BIOS level that prevent installing certain WiFi cards. The restriction can be bypassed with a BIOS modification: either installing Libreboot, Coreboot or editing the official Lenovo/IBM BIOS.

• Serial #, S/N: R9-V9ECF
• Intel Core i7-2620M processor (dual-core, 2.70GHz, 4MB Cache), DDR3 memory controller (up to 1333MHz), Intel Turbo Boost 2.0 (3.40GHz), HT technology
• http://shop.lenovo.com/ISS_Static/ww/wci/us/ww/pdf/x220_datasheet.pdf

I disabled hyperthreading in BIOS for security reasons, as well as the touchpad and fingerprint reader. I only use the trackpoint, and although the fingerprintreader is recognized, and software can be installed to use it, I disabled it for security reasons (fingerprintreaders are in general not reliable).

I replaced the storage with a solid state disk (SSD) from Samsung (840 EVO, 500 GB). It works flawlessly. I use a Kensington Trackball and a Happy Hacking Keyboard without any trouble, and use an external Samsung display, mirroring or not without any trouble.

Linux thinkpad 3.2.0-4-amd64 #1 SMP Debian 3.2.60-1+deb7u3 x86_64 GNU/Linux

Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                2
On-line CPU(s) list:   0,1
Thread(s) per core:    1
Core(s) per socket:    2
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 42
Stepping:              7
CPU MHz:               800.000
BogoMIPS:              5382.33
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              4096K
NUMA node0 CPU(s):     0,1

Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 004 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 003 Device 003: ID 13fd:2040 Initio Corporation 
Bus 003 Device 004: ID 147e:2016 Upek Biometric Touchchip/Touchstrip Fingerprint Sensor
Bus 003 Device 005: ID 0a5c:217f Broadcom Corp. Bluetooth Controller
Bus 003 Device 006: ID 04f2:b217 Chicony Electronics Co., Ltd Lenovo Integrated Camera (0.3MP)
Bus 004 Device 003: ID 1a40:0101 Terminus Technology Inc. 4-Port HUB
Bus 004 Device 004: ID 0e8f:0020 GreenAsia Inc. USB to PS/2 Adapter
Bus 004 Device 005: ID 047d:1020 Kensington Expert Mouse Trackball

00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
00:16.0 Communication controller: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 (rev 04)
00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network Connection (rev 04)
00:1a.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 (rev b4)
00:1c.1 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 2 (rev b4)
00:1c.3 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 4 (rev b4)
00:1c.4 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 5 (rev b4)
00:1c.6 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 7 (rev b4)
00:1d.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation QM67 Express Chipset Family LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller (rev 04)
00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller (rev 04)
03:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8188CE 802.11b/g/n WiFi Adapter (rev 01)
0d:00.0 System peripheral: Ricoh Co Ltd MMC/SD Host Controller (rev 07)
0e:00.0 USB controller: NEC Corporation uPD720200 USB 3.0 Host Controller (rev 04)

Slot:	00:00.0
Class:	Host bridge [0600]
Vendor:	Intel Corporation [8086]
Device:	2nd Generation Core Processor Family DRAM Controller [0104]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	09

Slot:	00:02.0
Class:	VGA compatible controller [0300]
Vendor:	Intel Corporation [8086]
Device:	2nd Generation Core Processor Family Integrated Graphics Controller [0126]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	09

Slot:	00:16.0
Class:	Communication controller [0780]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family MEI Controller #1 [1c3a]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	04

Slot:	00:19.0
Class:	Ethernet controller [0200]
Vendor:	Intel Corporation [8086]
Device:	82579LM Gigabit Network Connection [1502]
SVendor:	Lenovo [17aa]
SDevice:	Device [21ce]
Rev:	04

Slot:	00:1a.0
Class:	USB controller [0c03]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 [1c2d]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	04
ProgIf:	20

Slot:	00:1b.0
Class:	Audio device [0403]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family High Definition Audio Controller [1c20]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	04

Slot:	00:1c.0
Class:	PCI bridge [0604]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family PCI Express Root Port 1 [1c10]
Rev:	b4

Slot:	00:1c.1
Class:	PCI bridge [0604]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family PCI Express Root Port 2 [1c12]
Rev:	b4

Slot:	00:1c.3
Class:	PCI bridge [0604]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family PCI Express Root Port 4 [1c16]
Rev:	b4

Slot:	00:1c.4
Class:	PCI bridge [0604]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family PCI Express Root Port 5 [1c18]
Rev:	b4

Slot:	00:1c.6
Class:	PCI bridge [0604]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family PCI Express Root Port 7 [1c1c]
Rev:	b4

Slot:	00:1d.0
Class:	USB controller [0c03]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 [1c26]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	04
ProgIf:	20

Slot:	00:1f.0
Class:	ISA bridge [0601]
Vendor:	Intel Corporation [8086]
Device:	QM67 Express Chipset Family LPC Controller [1c4f]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	04

Slot:	00:1f.2
Class:	SATA controller [0106]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller [1c03]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	04
ProgIf:	01

Slot:	00:1f.3
Class:	SMBus [0c05]
Vendor:	Intel Corporation [8086]
Device:	6 Series/C200 Series Chipset Family SMBus Controller [1c22]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	04

Slot:	03:00.0
Class:	Network controller [0280]
Vendor:	Realtek Semiconductor Co., Ltd. [10ec]
Device:	RTL8188CE 802.11b/g/n WiFi Adapter [8176]
SVendor:	Realtek Semiconductor Co., Ltd. [10ec]
SDevice:	Device [8195]
Rev:	01

Slot:	0d:00.0
Class:	System peripheral [0880]
Vendor:	Ricoh Co Ltd [1180]
Device:	MMC/SD Host Controller [e822]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	07
ProgIf:	01

Slot:	0e:00.0
Class:	USB controller [0c03]
Vendor:	NEC Corporation [1033]
Device:	uPD720200 USB 3.0 Host Controller [0194]
SVendor:	Lenovo [17aa]
SDevice:	Device [21da]
Rev:	04
ProgIf:	30

00:00.0 Host bridge [0600]: Intel Corporation 2nd Generation Core Processor Family DRAM Controller [8086:0104] (rev 09)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: agpgart-intel
00:02.0 VGA compatible controller [0300]: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0126] (rev 09)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: i915
00:16.0 Communication controller [0780]: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 [8086:1c3a] (rev 04)
	Subsystem: Lenovo Device [17aa:21da]
00:19.0 Ethernet controller [0200]: Intel Corporation 82579LM Gigabit Network Connection [8086:1502] (rev 04)
	Subsystem: Lenovo Device [17aa:21ce]
	Kernel driver in use: e1000e
00:1a.0 USB controller [0c03]: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 [8086:1c2d] (rev 04)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: ehci_hcd
00:1b.0 Audio device [0403]: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller [8086:1c20] (rev 04)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: snd_hda_intel
00:1c.0 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 [8086:1c10] (rev b4)
	Kernel driver in use: pcieport
00:1c.1 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 2 [8086:1c12] (rev b4)
	Kernel driver in use: pcieport
00:1c.3 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 4 [8086:1c16] (rev b4)
	Kernel driver in use: pcieport
00:1c.4 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 5 [8086:1c18] (rev b4)
	Kernel driver in use: pcieport
00:1c.6 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 7 [8086:1c1c] (rev b4)
	Kernel driver in use: pcieport
00:1d.0 USB controller [0c03]: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 [8086:1c26] (rev 04)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: ehci_hcd
00:1f.0 ISA bridge [0601]: Intel Corporation QM67 Express Chipset Family LPC Controller [8086:1c4f] (rev 04)
	Subsystem: Lenovo Device [17aa:21da]
00:1f.2 SATA controller [0106]: Intel Corporation 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller [8086:1c03] (rev 04)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: ahci
00:1f.3 SMBus [0c05]: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller [8086:1c22] (rev 04)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: i801_smbus
03:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8188CE 802.11b/g/n WiFi Adapter [10ec:8176] (rev 01)
	Subsystem: Realtek Semiconductor Co., Ltd. Device [10ec:8195]
0d:00.0 System peripheral [0880]: Ricoh Co Ltd MMC/SD Host Controller [1180:e822] (rev 07)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: sdhci-pci
0e:00.0 USB controller [0c03]: NEC Corporation uPD720200 USB 3.0 Host Controller [1033:0194] (rev 04)
	Subsystem: Lenovo Device [17aa:21da]
	Kernel driver in use: xhci_hcd

Module                  Size  Used by
lp                     17149  0 
parport_pc             22364  0 
st                     34748  0 
ppdev                  12763  0 
parport                31858  3 parport_pc,ppdev,lp
bnep                   17567  2 
rfcomm                 33700  10 
binfmt_misc            12957  1 
uinput                 17440  1 
nfsd                  216167  2 
nfs                   308353  0 
nfs_acl                12511  2 nfs,nfsd
auth_rpcgss            37143  2 nfs,nfsd
fscache                36739  1 nfs
lockd                  67306  2 nfs,nfsd
sunrpc                173730  6 lockd,auth_rpcgss,nfs_acl,nfs,nfsd
loop                   22641  0 
snd_hda_codec_hdmi     30824  1 
snd_hda_codec_conexant    45307  1 
joydev                 17266  0 
usbhid                 36418  0 
hid                    81372  1 usbhid
sr_mod                 21899  0 
cdrom                  35401  1 sr_mod
uvcvideo               57744  0 
videodev               70889  1 uvcvideo
v4l2_compat_ioctl32    16655  1 videodev
media                  18148  2 videodev,uvcvideo
coretemp               12898  0 
crc32c_intel           12747  0 
ghash_clmulni_intel    13130  0 
aesni_intel            50667  0 
snd_hda_intel          26259  2 
snd_hda_codec          78031  3 snd_hda_intel,snd_hda_codec_conexant,snd_hda_codec_hdmi
snd_hwdep              13186  1 snd_hda_codec
snd_pcm                68083  3 snd_hda_codec,snd_hda_intel,snd_hda_codec_hdmi
snd_page_alloc         13003  2 snd_pcm,snd_hda_intel
rtl8192ce              60787  0 
snd_seq                45126  0 
rtlwifi                81393  1 rtl8192ce
psmouse                69265  0 
rtl8192c_common        52602  1 rtl8192ce
thinkpad_acpi          61270  0 
mac80211              192806  3 rtl8192c_common,rtlwifi,rtl8192ce
tpm_tis                17454  0 
snd_seq_device         13176  1 snd_seq
aes_x86_64             16843  1 aesni_intel
btusb                  17502  2 
nvram                  13049  1 thinkpad_acpi
pcspkr                 12579  0 
bluetooth             119455  23 btusb,rfcomm,bnep
evdev                  17562  24 
aes_generic            33026  2 aes_x86_64,aesni_intel
cryptd                 14517  2 aesni_intel,ghash_clmulni_intel
serio_raw              12931  0 
i2c_i801               16870  0 
cfg80211              137243  2 mac80211,rtlwifi
snd_timer              22917  2 snd_seq,snd_pcm
ac                     12624  0 
tpm                    17862  1 tpm_tis
battery                13146  0 
tpm_bios               12948  1 tpm
power_supply           13475  2 battery,ac
rfkill                 19012  5 cfg80211,bluetooth,thinkpad_acpi
i915                  378495  3 
snd                    52893  14 snd_timer,snd_seq_device,thinkpad_acpi,snd_seq,snd_pcm,snd_hwdep,snd_hda_codec,snd_hda_intel,snd_hda_codec_conexant,snd_hda_codec_hdmi
video                  17683  1 i915
drm_kms_helper         31370  1 i915
wmi                    13243  0 
drm                   183952  4 drm_kms_helper,i915
i2c_algo_bit           12841  1 i915
soundcore              13065  1 snd
i2c_core               23876  6 i2c_algo_bit,drm,drm_kms_helper,i915,i2c_i801,videodev
acpi_cpufreq           12935  1 
iTCO_wdt               17081  0 
mperf                  12453  1 acpi_cpufreq
iTCO_vendor_support    12704  1 iTCO_wdt
button                 12937  1 i915
processor              28149  1 acpi_cpufreq
ext4                  350763  5 
crc16                  12343  2 ext4,bluetooth
jbd2                   62115  1 ext4
mbcache                13114  1 ext4
usb_storage            43870  0 
sg                     25874  0 
sd_mod                 36136  7 
crc_t10dif             12348  1 sd_mod
thermal                17383  0 
thermal_sys            18040  3 thermal,processor,video
ahci                   24997  6 
libahci                22941  1 ahci
xhci_hcd               73450  0 
sdhci_pci              17976  0 
sdhci                  27053  1 sdhci_pci
mmc_core               68400  2 sdhci,sdhci_pci
libata                140630  2 libahci,ahci
ehci_hcd               40249  0 
scsi_mod              162269  6 libata,sd_mod,sg,usb_storage,sr_mod,st
e1000e                133833  0 
usbcore               128741  8 ehci_hcd,xhci_hcd,usb_storage,btusb,rtlwifi,uvcvideo,usbhid
usb_common             12354  1 usbcore