Win2K user here as well. The only reason I upgraded from W98 was because I needed to access files larger than 2GB. I could care less about XP and especially Vista (snort). Our laptop came with XP, and it's okay. Nothing I need to upgrade for.
The only time I needed XP was to try out Adobe Premiere Pro. Turns out the video stabilizing filter worked fine in Premiere, so that's what's on my desktop.