We sell Qmadix through our company. We love it, even if the liquid glass isn't 100% effective the 100-250$ warranty is where the product is paying for itself.
We've helped tons of customers with filing damaged device claims and the process is really simple. Send in receipt of repair or insurance claim, they mail a check.
As far as product quality, i believe that its beneficial but its not this magical liquid that will stop it from breaking, just adds a additional layer and more defense.