The 64-bit, GPU- and multicore-optimized Premiere Pro CS5 handles full-res HD footage with aplomb. The app features native support for video that comes straight off digital SLRs, as video evangelist Karl Soule demonstrates:
Update: If this is up your alley, see also these videos from Jason Levine:
Unfortunately, the screen capture program we are using sometimes drops frames during playback, so if the video didn’t look like it was playing at full frame rate, it’s the capture tool.
My Partner-in-Crime, Jason Levine, has some additional videos, showing keying and more effects using DSLR footage here:
http://vimeo.com/11775517
http://vimeo.com/11369451