Has anyone used "Quiet Rock" sheet rock in room?

Has anyone used "Quiet Rock" sheet rock on the walls and/or ceiling in their listening room? I am building a new dedicated sound room and I am trying to do all the "small stuff" (i.e. clean power and a well built/designed/acoustically treated room). All input would be appreciated.
If you end up dbl-ing up on the drywall make sure you buy the extra deep receptacle boxes with the nails set in the right place. If you don't and you start to cover up the walls you will have a giant headache. Standard depth boxes will be too far back in the wallboard and not pass code, let alone causing a ton of grief with covers & such. Speaking from experience of course doohhhh!
And if you have the money & motivation run some extra boxes with 1" flex tied to each one. That way you can pull cables and anything else through for a really clean look and convenience.
Good luck, John
It is expensive, but does work. However, you should consider what your goals are. Is it to isolate the room? There are less expensive ways to do this reasonably well and you will likely have other sound leaks--so don't break the bank on one aspect of sound isolation and forget another.

Second aspect, if you build a really rigid wall it will increase your peaks for modal response. Thus by isolating room in one particular method (stiff walls), will actual reduce the performance of the in room frequency response.

Check out our resources. You will find an article on sound isolation (right column) that may be of help to you.
So lets see.. I may be coming buy an unfinished Concrete foundation basement soon... Problem is I need FUll on un-comprimised sound isolation.. I am talking if you are running a live 120 db metallica concert inside it can't leak.. Basically you need the floors correct, the ceiling correct, all the utilities coming in isolated correct, the doors etc... No windows. Basically would be lets say a 16 foot wide by 20 foot deep area. With the cheapest possible material from the ground up design to make this thing whisper anywhere else in the house, or houses next to it what would be the overall average construction cost of such a project?

I am not talking excess designer costs, or full on room acoustic considerations... Just basic carpet, basic Door entryway, a couple electrical outlets, possible a single duct coming in right off the furnace in the basement right next to this room, basic lighting etc... Give us a ballpark here because I am always curious about this.. 10,000, 25,000$ ?

Rigid foam is a great way to go. You can get anywhere from 1/2 in to 2 inch in 4x8 foot sheets. I have this on the exterior walls of my house and you can't hear anything. You would just need to make sure you or someone doing the project understands vapor barriers.