I bought the Otterbox commuter case.
I think with cases it is always a compromise between protection and bulk, the Otterbox case gives the phone a pleasantly chunky feel. It's also very solid so should provide reasonable protection, though I haven't tested that yet. I like the rubbery lip it forms around the display. I didn't bother with the screen protector as I think they look crap and the display glass is pretty tough anyway.
The bad stuff: The outer hard case is a tight fit, and I think for this reason the inner rubber case deforms and make the buttons on the side difficult to press. I ended up filing out the slot in the case where the volume buttons sit, and also cutting away the "pip" on the inside where it pressed against the volume button. Also, several times I tried to squeeze it into the case, only to find that the phone had gone into safe mode because of all the accidental button pressing I had done in the process. How do you get it out of safe mode? Cover off, take battery out, repeat process.
I am happy with it now though...