I've got one and have been using it for about a year now. It's nice but not sure I would trust its fully waterproof claims. After a year the hinged lightning port flap had come off and seeing how the hinge works it's not particularly robust. I only use mine for riding so I'm putting the phone in and taking it out a lot. Maybe it would be better if you just put your phone in once and left it in permanently. Also if I make a voice call apparently it sounds muffled at the other end - maybe to be expected for a fully sealed and waterproof case. I've also dropped it from standing height and the corner snapped off, so it did it's job in saving the phone, at the expense of the case itself - which is what it's supposed to do I guess. So all in all if I'd paid full price for it I'd have been disappointed, but I got an ebay bargain for once (it is a genuine one) so I'm not too bothered, and it's still functional for protecting my phone when it's in my Camelback pocket with my car keys and multitool.
So on balance I'd give it 3.5 stars out of 5 taking into account the full RRP. 4.5 if you can pick one up cheaply. I don't think there are many options if you want a fully waterproof housing.