I will be opting for the ultra-lightweight BBS RI-D for summer tires, and the stock rims for my winter tires.
http://bmwi.bimmerpost.com/forums/sh....php?t=1327678
I like the idea of moving the rear rubber to the front (245/40/20) and either 265/35 or 275/35 for the rear. I am not a fan of understeer, hence prefer a more balanced front/rear size. Also not a fan of unsprung weight, hence the 17 lbs. rims and relatively light tires.