Sorry guys, it's been a while since I've been on the site.
After 10 months, I still love the suspension. I got to have my summer wheel/tire setup for, duh, the summer, which consisted of 225/40 and 245/35 Continental DW's on BMW Performance 18's. The grip was great although it made the 128i understeer quite a bit. Surprisingly, although the limits are lower, I have actually enjoyed having my winter setup (205/50/17's) back on. The car is just more neutral and there's the added benefit of better ride quality. I'll consider a square setup with wider tires on 17's in the future...if I don't get a 435i.
Otherwise, I have no negative comments about the B12's. I love the way the car handles. There is the tendancy for the rear end to be less than highly composed in corners with bumps, but that's a chasis issue from what I've read. The car is extremely fun to drive. I just wish I had enough power to make my summer setup understeer less often.
As far as the car, it squeeks more noticeably over bumps than it did with the stock suspension. It doesn't seem to have been made for a suspension quite this stiff (not that it is that stiff compared with most aftermarket setups).
I still recommend this setup to anyone