Anyone try Dynamat, HushMat or others?

I want to reduce the road noise in my car but I have no experience with these products. I talked with a stereo rep that showed me some HushMat. it was available in several different thicknesses. The 5/16" stuff was $189 per roll and it would have taken 2 1/2 rolls to do my car! Uhhh.... that seems a bit steep, right?
Anyone here tried this stuff?