I've had my S5 in a LifeProof since it came out of the box in the store.

I agree with Jeff's comments above- it does cut down a bit on volume, and I have to have it in just the right spot on my ear. Also I've had a couple comments saying that my voice sounds a bit muffled, but not sure I can blame that totally on the case. IMO if you put your phone in situations where it might get abused, it's the best case out there right now.