I think the actual Dashboard could be great. Granted I haven't seen it in full, I think the premise of a faster moving, more streamlined, and frankly less clunky dashboard is nice.
Ok, so they're mimicking the Playstation a tad by ditching the blades and taking this Media Centre-esque route, but there's nothing wrong with that. That's the way to progress.
I think the new features are fantastic, and give the 360 the boost that it needs. Party chat, burning the game to your hard-drive, etc. All great and good in my opinion.

I do, however, have beef with the avatars (who doesn't?). I'm excited by the thought of it, but the actual designs are awful.