Picked up my iPhone 4 today. Have to say, it does live up to the hype. Gorgeous screen and a solid feeling in your hand (that's what she said). I haven't encountered the two major flaws that have been reported - the antenna hand block issue or the yellow spot on the screen. Guess I'm lucky in that respect.
Photos with flash are really nice. Not great but waaaaaaay better than on the 3GS in low light situations. Haven't done HD video yet but will post some examples when I do. (with flash)
(without flash)