Havent had BC on my E92 but had the on an MPS... very very good value for money and great adjustability.
Currently have KW V1's on the e92 and they work perfectly for the road and for my time at the 'ring'. Although they are not adjustable in damping they seem to be pretty well balanced. Night a day difference in body control from the poor m sport dampers/springs.
The KW defiantly felt better around the ring than the BC's did, much more fluid, although it is a completely unfair comparison as it wasn't on the same car
If budget is tight BC's will serve him very well.