How do you folks feel about Dynamat-type sounds deadeners?

I'm about to put down some new carpet in my 68 Dart and am wondering if laying down some sound deadener would be worthwhile.

Also, I found this product on Amazon. Has anyone used it?

http://www.amazon.com/Noico-Self-adhesiv...=noico+deadener

http://www.amazon.com/Noico-Self-adhesiv...=noico+deadener

Lastly, do you folks cover the whole floor? Or scatter pieces throughout the floor?