If you're like a lot of people out there, you dislike the new Preview window in Column View. Why? Two main reasons: one you can't control the volume readily and two, there's no way to scrub through media there.
Scrubbing IS possible if you have an Apple Mighty Mouse. Just hover over the disclosed media in the Preview window and Scroll UP to go Forward and Scroll DOWN to scrub backwards. I have no idea how to do this using just the keyboard unfortunately.
One thing that bugs me about the new Preview window in Leopard is that you must click on the play button to start a preview's playback but you can click anywhere on the preview to stop it. That's inconsistent Finder behavior. And while I'm at it, why doesn't Quickview have a volume slider?