I have a 2003 M3 with SMG2. In "automatic" mode, occasionally when I come to a rolling stop at a stopsign or at a light, and start to accelerate just as the car downshifts from 2nd to 1st, it will buck off the line. It makes you look like you're learning to drive a stick-shift, which is embarassing. It basically won't stop until you let your foot off the accelerator and wait a second.
I have the shift timing adjustment set for the most aggressive mode. It actually does the same thing in manual shift mode, if you downshift from second to first and start accelerating just an instant after it shifts. It's as if there's a lag time for the computer to realize that the car's in first gear, and the ignition timing set set wrong by the computer.
Don't get me wrong, the SMG is a great transmission and I love the M3. This is the only problem that I've had, and you can learn to avoid it by forcing yourself to come to a complete stop. This is usually a good practice anyway, but sometimes the light legitimately turns green just as your coming to a stop.
I did talk to another 2003 M3 SMG owner who had the same issue, so I know I'm not crazy. I'm just wondering how many cars are affected and if there's any known solution (software upgrade, etc.) to fix it.
Dinan Stg 2 Phoenix Yellow M3