I ended up grabbing Ubuntu because the things I'd heard about it were all pretty good. Burned a CD, did the install, and it is really nice! Install was actually faster than XP, and it seems stable and runs snappy even on an older Pentium M laptop. The only fiddly thing was getting Wifi working, and that took a little googling to find the right driver, which installs as a debian package. In other words, you just click on a web link and open the file with the package manager, and it automatically installs. I also found Ubuntu Studio which uses the same package manager to install a complete suite of audio/video software.
If you've got an older machine around and want something relatively trouble free to use as an internet appliance or music production toy, you could do a lot worse!