Here's why I use Windows 2000-
It's very stable (runs fine for weeks at a time, not days). Memory and process management is also leaps and bounds ahead of 98/ME.
USB works much better than in 98/ME.
Game compatibility is a reason some people have problems with it, but those problems are few and far between. DOS games usually have to play without sound, and Red Alert 1 won't run, but most all windows-native software works great.
Drivers/hardware/software is maturing to the point where Windows 2000 is getting better performance in games than Windows 98. This also includes XP since 2K has less overhead.
Windows 2000 is Microsoft's "business" operating system which, historically, have better support, but also are supported for much longer.
My 2 zlotys.
/Atx