My truck has Dynamat EVERYWHERE in the crew cab. Inside door panels and door skins, headliner, rear cab wall, and floor with extra 1/2" of the foam matting that Dynamat makes. Took two guys all day to install.
Results are as above, and audio and conversation is a lot clearer. Sound levels went from 86 - 94 db (at 70 mph on smooth freeway) to 84-88 db. Most sound is now coming through the windows, windscreen and from the dash, which we did not pull. Mostly tire noise and wind from the tow mirrors. We did do the hood and replaced the factory hood liner. A noticeable, but not dramatic, difference.