Has anyone ever used Quietwood for underlayment?
http://www.quietsolution.com/quietwood.html
Wondering if it's worth the expense vs. plain plywood as far as noise dampening.

is a multi-layer engineered panel available in a standard 4' x 8' panel, weighs 170 lbs and is 1 7/16" thick. It is ready to use, and can be used in place of standard plywood, or above ceilings, below floors, or behind walls (finish with an outer layer of drywall). This product has one of the highest STC ratings (amount of sound isolation) of any interior wood system in the world. Using QW-640 with typical construction, walls and floors can be easily constructed with finished STC ratings up to 60, depending on construction techniques.





One 4x8 sheet is 170-lbs.

Still lighter than Maxxon gypcrete, which is about 7 lbs/s.f. at 3/4", so that's 224 lbs per 4x8

Plus, it seems like QWood provides equal or maybe better sound dampening. And you don't have to mess with mud & concrete. And nail/gluedown install becomes an option.