Incorrect. It should be full 1080p (progressive). And by the way, you shouldn't be editing footage straight from the camera. Run it through Neo Scene, get a file you can work with, and enjoy!
Another alternative you could try would be DVFilm Epic I. It allows you to start editing immediately without transcoding and creates RealTime Epic files at Full, Half or Quarter size so you can have realtime playback on practically any computer.
Vegas 10 is OK in that regard - but it has another weridness. it says the 550D footage is AVC, while V9 said its H264. i wouldnt mind whats displayed in the properties if the output would be correct.
but it seems is not.
test :
put a raw 550D footage into Vegas9, render it to uncompressed avi.
put the very same footage to Vegas10, render to uncompressed avi.
You don't need DVFilm, Cineform is fine. The bug is with the AVI container, no one's fault really. It's explained here, and a solution is shown too: http://techblog.cineform.com/?p=1407