Here are my first impressions:
- smaller and lighter than I expected
- lots of fingerprints on the demo, finger grease all over the screen -- I wiped it on my pants though and then it looked fine
- finger gestures become second nature really fast, and the single button "take me back to the main menu now" is surprisingly comforting to have
- others have mentioned this, but it's nice that when you reach the end of a list of things, if you continue dragging the stuff moves, but then bounces back -- "Yes, you can go that way, but there's nothing to see there..."
- very easy to get to everything, iPod music and video, phone calls, photos, internet, maps (which zoom in and out with the pinch gesture, very cool!)
- feels very un-complicated, which made me feel like "Is that it?" -- but after doing all those different things so easily (and without a manual!) that's a very good thing