I have a 545 without the sports package it handles beautifully. That being said, everyone I've ever spoken w/ who has the SP loves it. I personally did not care for the feel (or relative lack of feel) of the Active Steering. But that is me, plenty of folks love the AS. Go spend as much time as you can in both before making your decision. As for the runflats, I have heard lots of less than flattering comments about the ride and noise. Many folks have switched back to regular tires and have commented on how much better the car feels after the change.