I have a Decked System for my 2015 GMC Sierra 2500HD. We used it while we were full time traveling in our RV (2016-18). I also had (and still have) a cap on the truck. After we settled down I kept the drawer system installed for a few months, but eventually pulled it out because the loss of the bed depth (with the cap installed) became too much of an issue with day-to-day usage as a homeowner vice a full-time RVer (tough to put tall things in the bed). And, I was driving around with it mostly empty most of the time. With the exception of a three week trip to SoCal in winter 2019/2020, it's been stacked in my barn getting dusty. I've considered putting it up on the Marketplace, but I recently acquired a JDM van and thought about using pieces/parts of it to build out the van interior for camping and sleeping. However, I haven't gotten around to measure anything as I'm still recovering from achilles surgery and I'm a bit lazy...plus I'm not sure it would be the most elegant solution to that problem.
My thoughts on the system:
While traveling, it was great. Made organization simple and efficient. One drawer was devoted to fishing stuff and the other to camping stuff. I never had any water issues but again, it was covered by the canopy the whole time. I have the cargo tracks (I forget what they're called) installed and that made secure stowage of bigger stuff really simple. The loss of bed depth wasn't an issue because of how we were using the truck at the time. System is well made and drawers have convenient dividers that make things easy.
Day-to-day usage around the home, it was less useful because I had the canopy. With a canopy, for me it's less useful. If I didn't have the canopy, I think I would still be using it, but not 100% sure. I've had it in the back of my mind to pull off the canopy and just use the drawer system, but can't get myself to commit. What's stopping me is one of the regular things we do is take the recycling to the dump in town and hauling cardboard and the tall trash cans I use for aluminum, plastic, glass, etc. without the canopy and with the limited bed depth with drawers installed seems a bigger pain than I'm willing to put up with right now. Losing a good 12-16 inches of bed depth doesn't sound like a lot until you see it in action (photo attached to give some scale).
If I was a contractor or something like that and used my truck for work, then I think it would be great. However, there are some limitations to the size of tools/gear you can stow in the drawers. I think newer systems have the option one big drawer which would be better for bigger stuff.
Sorry for the long answer, but I hope this helps...at least somewhat.
View attachment 104472View attachment 104474View attachment 104475
The delivery guy had his trunk loaded and more bags in the back seat....and he had to park right next to my truck while unloading....a wee bit embarassing. 
That said, we quickly got over it and will likely never load the stuff on our own ever again.
