It really helps to reduce road and engine noise. Another benefit is it prevents rust! Just be sure that everything is fully prepped and they COMPLETELY hit the serious cancer areas such as the lower fender area by the cab and the upper front joint where the fender, inner fender, and core support come together. Rember that if assembled when done that the bolt heads will be covered, so that if you have to take it apart it will be a SOB to have to cut them out. You could A) mask the bolt heads B) have them sprayed off of the truck which is what I would reccomend, or C)just not worry about having to remove the bolts... just hope that no one hits your truck. Something to rember is that depending on how thick they spray the material can change panel alignment some if you do the panels seperately.
I plan on having the firewal, floor inner and outer, engine bay, fenders, etc done on mine when I get to the point. It should eliminate the big rust issues, as well as really calm the noise in the cab.