Maxamus,
win2k was reported to have 500+ bugs but in truth the asian technologies & advancement showing had some groups that found over 2000 bugs (but I wouldn't doubt if XP has more) & winME reported to have 16,000 plus bugs. Am sure we can't forget how many bugs win98 had (some 36,000+ bugs if not more by now).Most of these bugs are harmless, but little things can get in the way.
At a few offices here there are some 2000+ winXP pro installed units & 1000+ win2K pro units.
All seem to be working quite well. They both seem to be working on par with same speeds for office types of applications (as they use the same kernels for such & ntfs or fat32), but at the same time, the hardest working units here are the win2k pro units ('cause they have been around longer & have most of their issues solved).
I believe it has more to do with how your system is setup & what software/applications you use with your machine.
At home I have 1 machine with winXP, 2 with win98SE & 1 with win2K pro (linux machine moved to one office). No problems with any. Some have issues with certain things (win2k picky with DVD-ROM drives, while winXP picky with some older & new software, win98SE just picky lol), but after a little time spent on each, you get to work things out.
I prefer my winXP machine over the others (but could also be 'cause it has the newest hardware lol).
I still think people should just try them all out & see which they prefer. Nobody can say any OS by msn is bug free (not even unix is), just have to do your own tweaking & wait for fixes to come out.
Many just like the look & feel of one OS (especially gamers).
Still in the end, you can't go too wrong with win2K or winXP, 'cause I really think they are both better than any of their older brothers (though I know joripe likes his winME). =)