If you're thinking tarp and not a hard cover, I loved my Extang tonneau and would recommend one to anyone. Albeit on a Ranger and not an F-Series, it was great. Never tore, no issues with snaps, wore excellently and the frame was super easy to put on the truck. Even fairly easy to work with in the dead of winter. Had it on the truck 4+ years and no complaints at all.

I liked the fact that the bed was covered and kept out of the weather then, and I did get about a 1/2 mpg boost because tailgate drag was eliminated.

I am not really a fan of hard covers because I saw so many guys try to haul stuff in them and the cover was tilted up like an open trunk lid when stuff didn't fit under it. The Extang I could roll up, lay the supports to the side of the bed or in the back of the cab, and do what I had to do. But hey, to each their own. The hard covers can be painted to match if you don't want a black tarp (on my truck the black tarp was a nice offset addition though) and, as tylus said, some are stout enough to have some cargo strapped to them.

Just my 2 cents.