I currently drive an M5 coming from a E93 M, and I can honestly say that the M5 needs room to breathe to be able to drive it the way it was designed to be driven. I sometimes get frustrated commuting to work in the M5 because you only use about 10% of its ability. The M3, on the other hand, you can wind the S65 and get plenty of emotion and response from the car even in congested traffic!
I will echoe that the M5's passing power is incredible, you mash the throttle and you've gone up to 105 from 70 by the time you passed the car infront of you. That maybe why this guy was driving like a dick.