I have used a case with all my previous iPhones and have used lots of them. It is probably a good estimate to say I have wasted a few hundred dollars switching cases over the last few years always looking for the perfect case to compliment and protect my iPhone without ever finding one I am completely satisfied with.
I want to protect more from cosmetic damage than anything else as I am very careful with my iPhone and always use a "Death Grip" when pulling it out of my pocket for fear it may one day hit the pavement if i get to careless. In the last couple revisions of the iPhone, the plastic backing has been very prone to scratches. And keeping the chrome bezel scratch free? Impossible! The cases I have tested seem to contribute to these scratches just as often as they prevent them. But with the 4th revision of the iPhone, I think they have created a masterpiece that needs no protection from casual wear and tear.
Although I purchased an Apple Bumper case (pictured below) from the Apple Store on preorder day, after getting my iPhone and marveling at the beauty of my device, I don't want to cover it up at all. I want to look at it's stainless steel band with etched controls, not some plastic, rubbery case. So I have decided not to use a case and I am giving my brand new black Apple Bumper Case away. Will I regret this decision? Ask me again after I experience my first drop. Until then? Hell no!
So you want to win this case? Follow the @iPhonaddict on Twitter and leave a comment via Twitter or on this post about whether you are or going with a case or not on your new iPhone 4 and why. If you comment on the blog, just make sure you leave your Twitter username so that when I pick a random winner I can DM you and ask for your shipping info. Good luck!
Update: (08-01-10) Looks like Apple is giving them away for free! Can't get the Black Bumper? Hit me up!