Just got mine. It feels very solid unlike my previous Obex and Lifeproof. I even remarked about how heavy the box seemed. I haven't tried a phone call yet, but have played music through the speakers. Yes, with the lightning port closed, the speaker does sound muted. Its not horrible, but again the real proof will be during a phone call.
The one thing I am very happy about is that the lightning port opening is larger to accommodate cable adapters like the lighting to 30 pin adapter, which was not the case on the Obex. Also, the vibrate switch is easy to operate, also unlike the Obex.
The screen protector sits flat on the iPhone screen, and there is no pillowing unlike the Lifeproof. Its pretty responsive, almost as much so as touching the glass on a naked iPhone. No signs of oil slicks either. It seems to have some sort of coating on the interior of the screen protector that, I'm guessing, makes the screen protector not stick to the glass, which caused the oil slicks. Similar I guess to the dots on the interior of the Obex screen protector. The proximity sensor works without a hitch, unlike what I experienced with my Lifeproof case.
The home button is a little more difficult to operate with the case on, but its not too bad, just takes a little getting used to. Same with the power button, but I suspect that it just needs to be broken in a bit. The volume buttons seem responsive.
The headphone port is a little weird, not quite as easy as the one on the Obex, more comparable to the one on the Lifeproof. But, unlike the Lifeproof, the screw in headphone port cover is attached to the case so no chance of losing it.
In all, its my favorite of the iPhone waterproof cases that I've tried out. Note that I haven't tried out either the Otterbox or Atlas.