Amazing tech in this device. My Jaw hit the floor yesterday while reading the Engadget liveblog of the keynote. Holy crap, I do want one, but I really really REALLY wish they had put a SDHC or MicroSD slot on this thing. 8GB is a good start, but with video playback capabilities like it has, it's too cramped for storage.
Top 3 things that blew me away with the iPhone.
1 - Multi-Touch display... wow.. just wow... pinch to zoom.. WOW!
2 - Sensors - Proximity Sensor, Ambient Light Sensor, Accelerometer - again.. WOW!
3 - The Apps! - Safari, the coolest Google Maps I've ever seen, Push Yahoo Email, and on and on.. all based on OSX!
Top 3 things that I'm disappointed with the iPhone.
1 - No storage expansion.

I really want a SD slot in that phone somewhere.
2 - No 3G HSDPA network. Annoyingly slow if you can't find a wifi signal. Can you imagine loading a full non-mobile webpage over 50ish kbps. Yuck.
3 - No user replaceable battery. This bothers me slightly, but since we've never had an ipod with one, It didn't surprise me.