One problem related to transmission not engage has been reported for the 2009 BMW M3. The most recently reported issues are listed below.
This occurs regularly, perhaps 10 times per week or more depending on severity. On deceleration, the transmission will disengage the driveline. When the throttle is depressed again to accelerate, there is a long delay (greater than 1 second). This occurs at slow speeds (less than 20 mph), for example when entering a left turn lane with oncoming traffic. I had this behavior duplicated for a BMW technician who, upon further research, indicated that BMW was aware of this issue and has declared it "normal operation". It is only a matter of time before a serious accident is caused by this issue.