It's been 14 months since I purchased the $1200 steel jacket roll top cover from Pace Edwards, and I couldn't be more pleased. It's expensive, but the pay off has been huge and it does increase the value of the truck a little.
No leaks so far, the cover works as advertised with very little maintenance, and it secures the cargo bed. It's come in very handy when I was moving around all over the country and had to keep my personal luggage in the back of my truck for several days at a time. I do notice a slight vibration in the rear view mirror when traveling at high speeds, but nothing that is out of the ordinary for this model.
I've driven my truck through all types of weather...and the cover has sustained hurricane force winds in Louisiana, 14" of snow in Ohio, and over 100 degree heat in Georgia and Texas. The cover doesn't rattle, leak, and still looks great. My neighbor and my boss have bought the exact same model for their Tundra and F250.
The only problem that I've had with it is that the powder coated finish started peeling off this summer in some areas shortly after I got it, but Pace Edwards has been very supportive and is shipping replacement parts to me as we speak that is under it's generous warranty. I had a problem latching it one week, but that was fixed with a rag and a can of WD 40 being applied to the rails to clean them. All is good now.
I do recommend this particular brand/model if you are looking into covers. My next truck will have one.
http://www.pace-edwards.com/fullmetal_jr.html
It's very nice to have this lockable cargo area that can be retracted completely when I have tall items to carry, such as my ATV, extension ladder, or pair of black labs. It's priced slightly higher than the color-matching pop up covers, but it offers more if you are occasionally haul taller items.
Assembly is easy...more involved than a bed liner or tool box, but easier than a brush guard or trailer hitch. You will need 1/8" and 1/16" weatherstripping to water proof your tailgate upon installation...unfortunately, I haven't found a good way to weatherproof my tailgate in a manner that doesn't keep the dust out the back of the enclosed bed, but I have been able to keep the moisture out..
Gas mileage on the highway at a constant 65 mph is 24 mpg with the top up, 21 mpg with the cover retracted. I notice that around 74 mph, my truck returns to 8 cylinder mode where it will only run on 4 cylinder mode up to about 70 mph with the cover retracted. Those are not scientific test, but based on a stretch of highway that I travel often between Houston and Baton Rouge.
Hope this review helps if you are in this market.