The next best thing is to watch all the videos available on the web about Windows Vista at the moment. And believe me there are loads. First of all, the Windows Vista Weblog has links to a whole load of videos about various features in Vista:
I have to say the videos I found most interesting were the Aero UI video and the Sidebar and Gadgets one. There's lots of detail there.
There's also a video from Bill Gates CES keynote on the new features provided in Vista on the Microsoft website.
On a lighter note, going round the web recently have been a really funny set of videos comparing Windows Vista, due out in 9 months time to Mac OSX Tiger, which was released a few months ago. It has a guy talking about the new features in Vista whilst demonstrating the features on OS X. If you're only going to watch one, I'd watch the first one as I think it's probably the funniest, although they're all very funny.