I bought it on-line...don't remember now where. It was about a 25% discount verses direct from the dealer. It just looks like a roof rack! The pictures on the BMW website are accurate.
You have to set some plastic surface protecting pieces in the wells in the roof with some double-stick tape the first time you use the thing and adjust the exact length to fit across the vehicle, but other than that, the next time it just screws in with the included t-handled torx wrench (which is also a torque wrench!). The rack's feet sit on that plastic in the well which keeps the paint from being rubbed. Note, the skirt on the feet of the rack do NOT touch the vehicle's roof, only the feet that sit in the well, so the whole foot assembly sits above the roof a bit (maybe 1/4" or so - the body of the rails, maybe 3" above the roof).
I used mine to carry a recumbent trike, but it was quite noisy...I ended up getting a trailer hitch installed and now carry it in the rear in a basket- no noise or fuel penalty. Still, for a short trip to carry something bulky, it can be handy if it won't or you don't want to carry it inside. Not sure I'd want to carry something like a box up there on a long trip, but I'd expect it would be quieter than the open structure of my trike!
I'd read some reviews of (I think it was) Thule where their mount sits on the roof (but still anchors into the factory bits), but the feet dented the roof. I'd have otherwise bought the right feet for the bars I have (have both a Yakima and Thule mount for older cars) but instead sprung for yet a third rack system. The bar shapes are different, but you may be able to use some accessories with some creative attachments - I used the basket and used SS hose clamps to mate it to the rails.