I have a Thinkpad X220. First thing I did when I got the machine was load Ubuntu onto it. There were a number of annoyances: the machine got really hot, the fan stayed on constantly, the battery drained way quicker than in Windows.

But the most annoying problem was definitely the damn trackpad. The main problem is that it's horribly jumpy and unpredictable. No matter how I tweaked the options for the device, it would hop erratically. Most annoyingly, the act of lifting my finger away from the trackpad would cause the cursor to move. So, for example, I would move the cursor over a 'close window' icon, lift my finger to do something else (e.g. press a button/whatever) and the cursor would no longer be over the icon. I'd then have to reposition the cursor. So frustrating that I just gave up on the trackpad for a while and started using the trackpoint (which, I tend to call "the nipple").

Eventually, due to all of the problems taken together, I just started using Windows 7 (which, to my surprise, I actually like) with Ubuntu running in VirtualBox. All problems seem to be gone. Trackpad is totally fine in the VM.