Since you brought up the topic of wallets I suggest that you use only front pocket wallets as a rule. Experts say men who sit down with their wallets in their back trouser pocket risk damaging key nerves.
I have one of the piel frama 3GS cases and it is fantastic. I keep a couple of credit cards and my ID in the pockets, and the iPhone fits beautifully. Easy to slip in and out of the case as well (but it won't fall out).
Very well designed and manufactured, in my opinion. I have the magnetic closure model and have experienced no problems.