I bought this about a month ago (originally purchased the new version, as shown in the picture, then ended up returning it and getting an older version used for several hundred $ less) and have been very pleased with it. My first trip was skiing with 3 friends: it held my skis plus 3 boards, 4 pairs of boots, and my poles. The second trip was back-country skiing with a group of 13: I fit 7 pairs of skis, 7 pairs of poles, 3 pairs of boots, and 3 sleeping pads. Skis that are 185cm+ don't fit very well, but they can be squeezed in diagonally if necessary. The next trip was snowshoeing with a group of 13: I fit ALL 13 PAIRS OF SNOWSHOES PLUS FLOTATION TAILS! AND POLES! It was pretty amazing. Finally, it holds car-camping gear for 4 people. As you can see from the picture, I drive a subcompact hatchback. This box allows me to carry gear for 4 upstairs so that I actually have room for 4 inside, plus I can still open my rear door fully. I have not noticed any wind noise up to 75 mph and the mileage reduction is about 4 mpg (but is partially just from the extra weight of people and gear, it would probably be less on a bigger car. I go from 39-40 highway to 34-35).
My only complaint about the box is its weight, since the box alone is nearly half the weight I can carry on my roof- but I guess if it were lighter it wouldn't feel as stiff and secure. Also, because of the weight I need a friend to help put it on. With 2 people it takes about 30 seconds to place it on the rack and tighten down the clamps. The first fitting took maybe 15 minutes.
I lucked out finding this box used, but it is worth full price. It basically turned my subcompact car into a small SUV in terms of storage, for far less than buying a SUV!