I picked up the Lifeproof n??d about a week ago. My first impression was it did add a bit of width and height. After using it for a bit, I also notice how muffled the sound is coming out of it, although not bad.
I haven't had the complaints from anyone about sounding like I'm in a tunnel as some of the reviews have mentioned.
The best part about it is the screen is free from any screen protectors.
But as far as my opinion goes on it. I owned a lifeproof case for the 4. The sound gets really muffled when listening to music and talking to people. The nice thing about the nuud is the freedom of your the actual iphone glass instead of some cheap plastic covering it.