I do not have any experiance with them on BMW's, but I have been in other types of cars that have them. They are not quality products for auto-x or racing. A buddy with a 93 MR2 Turbo, belew his adjustable KYB struts 2x in one year. But never all 4 at once, so he replaced both times. He switched to bilstien and drove with them for 2 1/2 years with no problem. If all you do is drive like a communter, slow, no spirited or sport driving, and definately no auto-x, track days, canyon runs ect. then they *might* be ok, but I would rather go with OEM if that were the case (higher quality).
In short, I personally would never buy them for any reason.