*Update* this Apple video pretty much left me mesmerized, go here
Battery is 16% bigger than the current one, Apple claims 40% more talk time.
The display will be four times more beautiful and clear than ever before. It's like holding a magazine in your hand.
The camera is now a 5-megapixel device backlit, and it has bigger lenses. It has a higher ISO—or sensitivity to light. That means you can take better photos and video in low light conditions.
You can record video in HD quality. 720p at 30 FPS.
FaceTime video calling from iPhone 4 to iPhone 4 (over Wifi network only for the time being)
Multi-tasking. Switch from app to app without closing a program. Fucking awesome.
All in all, I need one yesterday. Apple is the greatest.
Gizmodo iPhone 4 Definitive Guide