I dont think anyone realizes that there are a lot of threads about grey cladding. Nothing will stick to it. Everyone that paints it says that if chips right off. Bedliner has worked for some, but not others. Its almost like it has a light wax coating.
Personally, its not for my truck. I can see the advantages though. The cladding is THICK, so it makes the truck a good 3''+- thinner. Now there is no worry of messing the cladding up offroad, and it can always be reinstalled if you change your mind. (Assming you dont sell it all lol).