I was out with friends and set my 3 month old iPhone 4s on my purse (which was apparently slanted). It slid off onto the concrete floor. At first I thought nothing of it since I had dropped my iPhone 3G a lot with no damage. When I picked it up the back of the glass panel was shattered. BOO :-( The phone still worked fine but the little shards of glass coming out were a problem.
Piece of cake. Removed the screws, slid off the panel put on the new panel and wa-la... good as new. It litterally took less than 5 minutes!!!
I see bumpers or a case in my future