I have the Commuter and am very happy with it. Provides a much better grip so Im not quite as paranoid about dropping it if Im holding it while walking.
Can't speak for anyone else, but I haven't noticed any looseness around the volume buttons like you mentioned.
I haven't used the screen protector as I don't keep my phone in a bag or the same pocket as my keys, and there's a good 1-2mm of raised case around the phone so even if I dropped it face down, Im confident it wouldn't damage the screen at all.
The phone does feel a bit heavier and bulkier with the case, but I can live with that for the added protection.