Some things in RDP that will be improved in Windows 7:

• Aero Experience
  like translucent effects, previews
• Direct 2D & Direct 3d 10.1
• True MultiMon Support
• RDP Core Performance Improvements
• Multimedia: Media Foundation
  Running Audio and Video smoothly
• Multimedia: DirectShow
• 40% gain in bandwidth reduction

I’ve seen a demo where they played a video (1080p), the audio was a little behind on the video (but not irritating slow), the video was really smooth and the processor load on the server was only 1%.
Want to see it for yourself? Check out this link, @ 22min. it is playing the video, and @ 23min, it plays the HD movie.

My opinion: impressive, I know some company’s who really could use it.