Does Dynamat really work??

ive never used ot, or even heard a car with it in it, my my MTX T6000's are starting to make my trunk fall apart and sound like i have rocks in my lid...my friend suggested dynamat, but i dunno (he's not all that smart, ran a 4wd explorer into a mud puddle and killed it (theres a ford for ya))

but before i even buy the crap, i would just like some feedback as to its actual ability to make me not sound like a poor white boy, shut up :-P

and i think im gunna install it myself cuz them sleezy rip offs at circuit city want like 35 bucks for installation....

plus, im almost sure its just my lid vib. so thats all i really should cover right?

also, if i do this, its not permanant is it?...i mean, im thinkin of gettin some sweet tail lights in the future also, this would hinder my ability to do that would it?