I have the Ford retractable bed cover on my Ranger - the OEM is Retrax. This one is the aluminum; they make a polycarbonate version that is a bit less.
So far I am very happy with it, and have a Yakima Overhaul HD mounted above. The overall quality and finish are excellent. It is supposed to be able to hold 500 lbs (dispersed) - before buying the truck I did climb on top to make sure it held my weight (~215). Not sure I would put that much in any one spot while underway. It is really fast and easy to open and close (so far) and I love the ability to access pretty much the entire bed quickly. And I have significant peace of mind when leaving valuable bits inside compared to any other cover/topper I've used before.
There are a few "nits" if I am being picky....the stock drain tubes coming out of the bottom of the "house" for the retracted top keep getting knocked out when I am less than careful about throwing things into the back of the truck. I have purchased elbow fittings to help route the hoses a bit better. The cover for the lock looks like durable rubber, and it slots down around the lock, but I am concerned that it will dry and shrink over time. The Ford version only has one locking position (fully closed). I think the regular Retrax has the ability to lock pretty much anywhere along the run. I may drill a few additional holes (fully open, open 2", etc.).
It weighs in at around 65lbs, which is a bit heavier than the tri-fold I had on an earlier truck. It takes up about 3/4" from each side of the bed, about 12" from the front of the bed, and the house sticks down about 10" from the top (at least on my truck with a 6'1" bed length).
Let me know if you want any other pics or measurements.