I tried a Lifeproof case with my 4S last year and the gap between the phone screen and the case screen made tapping impossible! I took it back to Best Buy immediately. Unless you're using your phone in a very risky environment, it's a deal breaker. Doesn't sound like their iPhone 5 case is any better, but I haven't tried it (heck, I've discovered that the 5 must stay naked unless, as I said, you're in a bad environment).
Except for risky jobs or extreme sports or whatever, I can't see why anyone would use this case.