I previously owned the LifeProof for iPhone 5 (the newer color ones). I experienced no issues except a slight oil slick effect on the screen. Screen sensitivity wasn't an issue at all for me either. It was a great case but I wanted to try other cases before settling on one for rugged use.
I'm currently using the Incipio Atlas and have no issues with this case whatsoever. It's like a LifeProof Fre but with a tempered glass screen protector. I haven't run into any audio issues because I use a Bluetooth headset, speaker, or my deck (via Bluetooth) to listen to music while in my car. The same goes when I owned the LifeProof (Bluetooth for everything).
I'll be sticking with the Atlas for now until it gets beaten up to the point it needs to be replaced.
Have you tried using the case's earpiece to talk on the phone instead of bluetooth?
For me, it was ridiculously diminished when someone was trying to listen to me talk. Plus, when I listened to someone else talk, it had some feedback issues.
I have to admit, the case is built very sturdy and won't scratch easily like the lifeproof, but I couldnt handle not using my phone to talk.
I switched over to lifeproof instead, and although the oil slick and puffy screen annoys me, the sound is great, both from speaker and earpiece.
BTW, why hasn't Lifeproof annouced anything about the release date of the nuud?
Bestbuy says its 7/7, but I havent heard any feedback from lifeproof.
I hope they don't delay it. IMA BE PISSSSSS :O)