Win2k is a damn fine program once you get it up and running for a while. Honestly it has been my misfortune to discover that Win2k desires a "break in" period before it will run smoothly.
98 and 98 SE were good programs in there own right if you didn't mind the BSOD every 12 hours of continous operation.
Win2k has performed very well for me, and I have spent a lot of time getting it to work well with my AMD Atholon. (NOTE: I even used up both of my free MS help sessions to get it too work smoothly. Simple stuff that took about 4 hours apeace to fix.)
Right now, I am considering XP. I thought I would wait until I needed to build my next super system before venturing into XP territory.