I find just exporting the X session over ssh is usually faster then using VNC or an external app. Just use the -X -C switches (export X, use compression).
Doesn't that only allow you to run one X app at a time?
Nope. It just carries the X protocol requests from the remote box to the local X display, so you can run as many as you want.
There're actually a number of ways to do remote displays:
* ssh's X forwarding only works with OS's that use X displays, of course.
* Windows displays can be exported using Windows' native Remote Desktop Client protocol ("RDC") with a Windows client or with the freeware "rdesktop" client.
* VNC has the advantage of having been ported to quite a few kinds of displays.
You can mix and match any of those that fit your needs at a given moment. There may well be other choices, too.
VNC is not performing that great for me even in testing on the same box. I mean I can tell the difference in speed and I think I shouldn't be able to. Functionwise it's great but it's slower than it should be.
Slower than it should be? Not necessarily. Sure, it's not as fast as we
want it to be, but consider: You're using software to watch the windowing system for changes as trivial as mouse motions, package them up and ship them over a network link (even if the link is on the same machine) and draw them remotely. VNC is not native to any windowing system, and has to tie into them using tricks specific to each, some of which can be pretty ugly or inefficient.
RDC is pretty efficient for Windows systems, which is not too surprising as it's built directly into Windows by Microsoft. I can play video through it (!) without much pain (excepting that I haven't tried to figure out the sound set up through "rdesktop"). That is, you can tell the difference, but it's pretty good.
My recommendation is to use ssh for X, RDC for Windows, and VNC everywhere else.
EDIT: for clarity, I mean: "ssh for remote boxes that use X, RDC for remote Windows machines, and VNC for anything else or where ssh or RDC don't work for some reason."