I hackintosh'd my x220 to the latest Mountain Lion. My only real problem was getting sleep functionality to work, but I didn't really see others with my problem and didn't post asking for help. I had to buy an alternative wireless card (Dell 1515) for $10 off ebay, as the included chip doesn't have OSX drivers. It probably would have been fine for at least a couple months if I had spent more time fixing the sleep issue. Except for that, it worked great, and it wasn't difficult to add drivers or processor power management stuff.
I switched to dual-booting Ubuntu and Windows 7, but will either switch back or buy an Air in the future.
I switched to dual-booting Ubuntu and Windows 7, but will either switch back or buy an Air in the future.