I bought this case as soon as I had my new phone. The galaxy s2 is very thin and I didn't want any damage done to it if it was dropped etc.
This case is brilliant! very tough, feels nice and is great quality. I have dropped my phone a few of times since having it and it just bounces with the case on, no damage was done at all.
Comes with two layers, a soft rubber innner case and the thicker and more solid outer case. It also protects the front by the small rubber lip being higher than the front screen, if it lands face down the screen isnt touching the floor.
I would highly recomend the case mate brand and this particular case especially.
I have also got the clear screen protector that you stick on to avoid any scratches to the screen, worth buying to protect the front as well just in case.