@hp 246: Yes, it works great on duct work.
I think the problem with most sound deadeners/heat shield/ insulation products is that everybody tries to cover every square inch with it. Anything will work to some degree. I just got some stuff called trunk liner that is about 1/8" thick and has a peel and stick backing on one side and a fuzzy surface on the other. It's only 10" wide, but I'll bet it would do a good job of insulating and noise reduction. It sticks like crazy, and it was really cheap. Here's a picture:
No one lives forever, the trick is creating something that will.