I use win2k but have thought about upgrading to XP since I can get it for free from school.
I've joked with my friends that XP is "2K for dummies"
The only differences that appeal to me in XP are:
the better text (cleartype or truetype or whatever its called)
the new start menu design (I hate desktop icons)
better customizability
Today at work I got my first exposure to XP home... yuck is all I can say. I felt so crippled by it, way too sugar coated.