From Car and Driver's long-term test article on the 2008 M3 DCT at 40k miles:
The only significant complaints involved the dual-clutch transmission. In automatic mode, it works remarkably well, and it was hard not to be awed by the speed of the shifts and its smoothness of operation. Indeed, technical director Dave VanderWerp observed that it “upshifts so smoothly under part throttle that it’s easier to detect a shift from the change of the exhaust note than it is to feel it. Too bad,” he went on, “that the lazy throttle tip-in from standstill is so off-putting.”
And near the end, the dual-clutch transmission was making clunks and groans. Assistant tech editor K.C. Colwell was adamant that the transmission had loosened up considerably. Twice while the M3 was parked facing downhill, the transmission slipped markedly when the driver was trying to back up. If the clutches need to be replaced, our local dealer quoted us $3296 for the job! So far, none of the M3 forums has reported any issues with M DCT, save for the service bulletin already mentioned. Indeed, most owners seem besotted with the dual-clutch gearbox.
Most of the sentimental drivers on staff would have preferred a manual transmission in the M3, although the automatic function of the M DCT is good for mindless commuting.