I have not used TeamViewer but I regularly use iTeleport in a local WiFi network situation. I have not tried running remote session over the wider internet through a SSH connection.
I also have RemoteTap which needs some serious work before it becomes really as viable as iTeleport.
Mac OSX has a built in VNC screen sharing service. I don't think Windows does, which is likely a good thing for all.
I'll give TeamViewer a try now, however one thing I really like about iTeleport is its option for both a tap mouse and a standard mouse (the mouse stays on screen and you can drag it around like a track pad). That track pad style mouse helps take out a great deal of inaccuracy when doing fine manipulation.
I totally agree, bigger screen on iPad will be better for all remote PC viewing/control programs.
*edit*
Okay for the free version its not to bad...
Has the track pad like mouse control by default which is a plus. Zoom button seems redundant until you realize the pinch zoom is sluggish and inaccurate. No multi-monitor support, requires switching in the settings (shake iPod for quick switch, guess its okay as a bandwidth saving tactic). Keyboard is interesting and auto adjusts to rotation, they could have picked a better keyboard close icon which looks like the eject button on a Mac (not smart). Removes the background of the monitor you're primary viewing (on mac) and replaces it with flat blue (a good bandwidth saving technique for other remote control program use, although possibly annoying from an esthetics sense).
I need to test more on pushing the connection speeds and run iTeleport under the same encryption. Then again for a non-commercial use free program TeamViewer isn't to bad for basic uses.
My main test for most remote control iPod/iPhone apps is how well they transmit and render while Flash videos (singular) are running. Aside from the control feel it's a good test of both connection speeds and rendering ability at a very high level.