Hmmm though question. Althouh I know quite some ppl that prefer XP strongly above 2k, I can't find a way to get XP to work I want.
A really good and strong point of XP is the immensive build-in hardware database. A wide of range of products is supported. Just hook up your camera, printer, scanner or whatsoever, and XP'll probably support it (as long as you've got a decent brand).
2k Is way compacter (saves diskspace

), is faster (although for me), has less crap in it (no text balloons popping around the screen), has better memory managment etc etc... yes 2k for me..
But I guess there'll be enough ppl telling the same bout XP....