I am a deck contractor. 80% of all my decks are built with pt wood. 15% cedar, and 5% redwood.
Where i live, there is a local Payless Cashways with a 10x10 deck built with Trex. The rep. had one built there for exposure and to show it off. The retailer had to pull it off the premisis because the planks were buckling and bowing. You have to realize in Texas in summers, the heat is grueling and punishing to everything it touches. The Trex deck did not stand up as it should.
The lumber is so expensive, I could never understand why someone would want the stuff at that price unless money was no object. PT wood and redwood lasts for 15 years and 20 if properly maintained. So what is the problem? you could build three 10x10 decks with pt wood with the same amount of money to build one Trex deck.
I just do not think that Trex people did enough R&D to justify a lifetime warranty.