Provides surprisingly good grip - if the phone slips you will catch the elevated edge.
Very tight fit - feels almost like a part of the phone.
Good protection - thick rubbery plastic (or plasticy rubber?) elevates the phone and provides good protection from all sides. Combine it with good screen and back protector and you can be quite relaxed using your expensive toy.
Phone still feels thin and light which is an important feature of No.5 - no sacrifise there.
The edges feel a bit too high (compared to the iphone4 models from this side) - good for protection, but it just feels a bit too much. And it's just my feeling.
The surface/texture feels a bit too rough, especially compared to the refined feel of the phone itself. Again, it is not that much of a problem, more of a feeling.
All in all, usable and enjoyable product, especially for it's price.