I think deciding a case for this phone will be harder than the 3G. With the design of the 3G I didn't mind covering the sides, back and some of the front since i wasn't crazy about the silver border thing. With the iPhone 4, from looking at pics, i think the design is much nicer and the antenna border and buttons are so nice looking, i really don't want to cover it up. Which is why i don't like the bumpers. Maybe something clear would end up being the best choice.
EDIT: I'll be keeping an eye out for something eco friendly from Agent 18.