I have owned an M-5 for about 6 months now. I can say, I cannot go back to an "ordinary" BMW. The car is the most fun thing one can do with shoes on. It does drive a bit jerky at slow speeds, but I will say, it was not meant to go at slow speeds!. On a serios note, the SMG takes a little bit getting used to. I find manual to be a lot smoother. The only down side it gas milage, I am aroung 14.6-15 mpg. But it makes a statement, and turns heads whereever it goes. I love the growl it makes when I downshift.
For all the folks who want an M experience, once you drive one, you cannot go back!