We just launched a remote desktop app - Splashtop Remote - that's pretty different from other iPad apps folks have talked about so far. The app is optimized for video and audio, so you can get a fully interactive experience - down to playing casual games with minimal lag. Unlike RDP apps, Splashtop Remote requires a software component to be installed on the PC, which at this point only works with Windows - Mac version on the way.
Sorry for a "shameless plug", but I think this is relevant to the thread.
note : tested on a very fast network sitting close to router with ipad, computer is on ethernet, same local area network. this is a setup ive optimized for very fast jump performance.
okay i am VERY impressed with the video performance. it is actually smooth and very good quality. definitely better than jumps choppy video. the audio sync is not there though, which sucks. if it had audio sync perfect itd be really great. still great potential but a lot of work needed:
-why cant i rotate the display? if anything, turn the default the other way, as when flat on a desk with apple case the screen is sloping downwards away from me, not nice. but ive just realized that this is nicer for on leg/jean use, lol didnt realize this before.
-desperately needs a mouse circle a la jump. frustrating to try and use mouse accurately.
-change two finger scroll so its not reversed!!!! i dont like this backwards setup.
-keyboard needs more layers so all the controls are there, like i cant alt-tab right now.
-performance aside from video is not as good as jump. pretty good, but definitely not as fast. if the mouse circle was there itd be muchhhh more enjoyable.
basically copy everything from jump and add the great video performance

and sync sound to video.
i do like the little keyboard key and its location, thats nice.