Ubuntu
I've officially jumped on the Ubuntu bandwagon! I definitely like it. The GNOME setup is really sweet, although as usual I've already built GNOME myself so the niceness is somewhat diminished. I hadn't tried hal/gnome-volume-manager before, so it was a pleasant surprise to see my usb drive automatically appear on the desktop as I plugged it in :) The overall amount of tweaking to get a nice system is a lot less than the regular debian installation, so I'm happy.
Other good news: the PowerBook heat situation is a bit better now that I've started using cpufreqd, which is nice. Hopefully the battery time will improve a bit too. I'm looking forward to the rewritten therm module in 2.6.10-rc which I think will probably make things even better since it makes better use of the fans.