I have not driven my truce since I installed them, so no info on the additional sound deadening yet. Maybe Dave can give an update on that. Overall, they are very good quality and fit very well. They are made of very high density material (which if why they are very stiff) and have a mold release agent on them (which is why they are slimy). Since there is nearly and infinite number of possible configurations for Defenders, they need to be modified to fit. Trimming, cutting holes and openings, and removal of the interior is required. Once complete, you need to let them sit overnight to "settle", then they fit very well. I wanted a seat box cover, and theirs is very nice. It really finishes the interior, albeit with rubber.
Is it worth the cost and effort, well that would be up to you. I am glad I did it.