Yes I have one, a couple buddies do as well. Nice units but my biggest complaint was the latches working loose on rough roads. Got back into sledding so I went back to a deck.
They can be hard on the body of the truck. If you're not keeping the truck for long, then it doesn't matter. I've seen GM boxes damaged so badly that the tailgate won't close. And your expensive toy is held to the truck with the same aluminum clamps that hold toppers on....
IMHO a deck that's bolted to the floor of the truck is stronger and safer.....
Ive had mine for almost 7 years and regularly load 2 quads on it with NO box issues. I don't have a GM and i do know they require a bed stiffening kit for the centre pannel as the plastic bed rail is not stiff enough . But I have not heard of any other trucks having the bed sides bending or the cover tearing off or anything eles that non diamondback owners try to claim. I believe there are other threads on this topic with many other owners sharing there experiences.