I have an Ubuntu 6.06 LTS install on a secondary hard drive on this computer. I like it because it is really user-friendly (although there are still major differences between this and the Windows XP experience), and it is generally easy to operate.
I have had problems with it, but that is probably due to the fact that in Linux one does tend to have to know a lot more about how things work than when using Windows XP. (One example is the "xorg.conf" file to set up multiple monitors; it took me a while to
do it, when in Windows XP it takes about 30 seconds).