The more I use Remote Desktop on XP, the more it pains me to go back to VNC. Not that I don't admire VNC - it's a phenomenal tool, especially if you need to go cross platform (where cross platform can mean as little as "not XP"). Super light-weight, super easy to install (and the viewer piece doesn't need an extra install at all - in fact, it's entirely optional if you want to use the web browser client). But the seemlessness of remote desktop can't be beat. As a heavy keyboard user, I find VNCs less-than-complete support for keyboard navigation problematic. I need my Alt-tab and Ctrl-Esc, dammit! Also, the full screen mode of RD makes the illusion of local access nearly perfect, and the ability to easily share local resources with the remote machine is very handy.
Now if only XP Home supported it so I could do proper remote tech support for my parents.