<<The cool thing is MS is making XP better than Win2000, so even Win2000 users will have a reason to upgrade.>>
Well, lets take a look at MS's os history: (9x Kernel)
Win 95 A
Win 95 B
Win 98
Win 98SE
Win ME
ME was supposed to be better than 98SE, yet it's plagued with more bugs and bloatware than ever before and removed many options that helped tweak your system, so that those who don't know much about computer don't mess up the OS. Most will agree that ME not better than 98SE (while comparing 9x kernel OSes)
Now look at the NT History: (Starting at NT4.0)
WinNT 4.0
WinNT 5.0 (Windows 2000)
WinXP (Basically, this is Windows 2000 ME)
According to information about XP, MS toses in some more applications that advanced users will never use, more restrictions, (ie. Content Control) make it more colourful with more active desktop like features, in result using more RAM (using ME as a fine example). In addition, 2K already has great compatability. Lastly, with the new protection system on XP, if you add HW, and reformat you gotta call up MS. Also WinXP doesn't give Win2K users a reason to upgrade because 2000 is overall the best OS ever released by MS (with Dos 6.22 as the exception). 2K isn't full of bloatware compared to the new "user-friendly" MS OSes, and has high compatibility with software/hardware.
Mind you, that's just my opinion.
--Mark