I just went to the apple store and picked up the Mophie juice pack reserve it's pretty cool and it has a built in flashlight also. Even though the iPhone 4 has excellent battery life it's still good to have a way to keep it charged around
. I love mophie products and i had the juice pack air for my 3GS which lasted untill my mini-usb broke on it 
Which batteries do you guys use if any?
Which batteries do you guys use if any?