I'm curious: how long have you been running Ubuntu on your X220? And how stable has it been?

I was using Ubuntu on an X220 as my development machine for a while, with Ubuntu 11.04. It was extremely unstable -- the machine would freeze frequently when unplugging the DisplayPort cable, or even right in the middle of working. That along with a host of small bugs and annoyances (invisible desktop space on the smaller display in dual-display mode -- a longstanding issue in X apparently) eventually drove me back to using a Mac.