Have you tried VNC? Besides the slow refreshing, I think it is better than Terminal Services, pretty much solely because you can send ctrl-alt-del to the terminal, so you can lock the remote NT/2k computer. And it's available for many OSs, including Mac, but dosn't seem to have a port yet for OS X. I've used it under WinNT, Win2k, and Solaris 8.
-Ken