Seconded!... uh thirded?
I havent and will not touch anything older than win2k at this point.
Started running win2k pro when it was in beta, and have been running XP for a year-plus with no complaints or problems. My system is a P4 1.2ghz with 1gb memory, and a 64mb geforce. Everything runs great.
Even after bitterly complaining about the "fisher-price" look. I tried it out for awhile, just to see what MS was thinking, and it actually works pretty well.
Once you get used to it, and learn to open your mind.