I had a Bak F1 in the past and was happy with it ('11 Tundra Crew Max, short bed). I currently have a Bak HD and am grossly disappointed so far in the cover, and in the customer support. I have a warranty replacement cover arriving tomorrow (my original cover was bad out of the box, no confidence as of yet that the new one will be any better). They claim that the covers for beds longer than about 5'9" (they won't commit to an actual size) are four panels and not three to adhere with a supposed federal law/regulation prohibiting the high-mounted stop light from being covered when it's folded up. But, the UnderCover covers are ALL three panel and use the same 4" wide panel at the front to anchor the cover in the first place.
The Bak HD I currently have leaks at the bulkhead, leaks along each side rail, and leaks at the tailgate. It doesn't sit flush and smooth along the length, the rubber seals have not settled out flat (and it's been on the truck a month), it doesn't fold up smoothly, and I absolutely can't stand that the third panel does not latch to the rail.
The fact that Bak provides no actual technical details (measurements) of the covers, does not indicate that all covers are four panels except for the one for the short bed, and they do no provide ANY vehicle-specific installation instructions is bad enough - their terrible customer service throughout my experience so far has left me feeling like I absolutely NEED to find a different cover and sell this one off before it breaks and they won't honor the warranty on it.
The roll-up covers are useless to me (completely open or completely closed are not the only two options that I need, and giving up bed space won't work for me because I must be able to access the area of my bed all the way to the front). Fold-A-Cover's "you'll just have to take it off if you need access to the whole bed" process doesn't work for me, and I'm skeptical as to the cover over the lock not causing problems during the winter. Cloth / vinly covers just flap around in the wind and make noise and they don't provide any security for items in the bed.
IMHO, the UnderCover cover would be ideal if they'd get their head out of their a$$ and lengthen it by two inches for the 6'6" bed.