I’ve been using Ubuntu at home on one of my computers for close to a year now. I’ve been pretty happy with it, although Gnome struggled on my computer (a circa 2003 Athlon). Switching to Xfce fixed that, and my one remaining problem was Firefox.
For those who haven’t tried Firefox 2 on Linux, it’s pretty bad. If leave a Javascript heavy site (eg GMail) open the browser will slowly grind to a halt over a course of a few hours.
I recently upgraded to Firefox 3 (see this video for how to do that), and it’s made a HUGE difference. The one issue I had was that I could get it to start - I hadn’t realized that the executable was now firefox-3.0 instead of firefox. Makes sense, though.