Thanks for this reply. Just to clarify something though, I'm not anywhere close to "jumping on it" when this happens. It's literally at maybe a little more than 1/3 throttle when this happens. Think of it as accelerating moderately to blend into traffic.
I've got 2300 miles on our S650 and I'm experiencing some strange shifting behavior when the car is cold. After starting the car and letting the idle settle, if I give it 1/3 to 1/2 throttle as I pull away, the transmission stumbles pretty badly between first and second and again between third...