I had one.
It was OK. I wouldnt get one again. Always freezing up in the winter. Ice in the lock (vertical facing lock, wth??) and ice in the side rails. Plus the roll area behind the cab took up a lot of bed space and would also gum up with snow and ice.
If I lived in Florida and could deal with the loss of box space (both length and width) Id get one, but im my experience it was overpriced for what it is, especially if you use your truck (ie: need the full bed, like for an ATV) and live in a place that sees winter. I was never so happy as when I removed it.
If I was doing it again, Id get one of those hard cover, Tri fold style. At least then you could use all the bed and they are easily removable when needed. Plus they are easy to keep freed up in the winter.