Here's my $.02! My truck came with the Ford drop in liner and the Ford roll-up tonneau cover. I got tired of busting the crap out of my knees when I had to root around in the bed so I used these foam interlocking tiles (Foam Tiles). For me they work great! Makes it nice for my truck bed tent...
My Dynapro LT"s have a little over 17k on them and I'm not sure if they'll ever wear out. They came with the truck and I don't tow so I'm leaning towards replacing them with something that will give a softer ride. Life's too short to not get what you want!