DCT on the 335i goes like this:
1/ Start up from cold. Sometimes it acts like the old six speed and moves without the brake being applied. On other days it won't move until the accelerator is applied (more often than not). Is this the same as the M3?
2/ During normal driving you are sitting at say 60 in 7th gear and then you floor the accerlerator.What happens is the revs immediately jumps from 2000 to 6500 revs approx and then it changes into 4th a second later. Feels like forever. Does this happen with the M3?
3/ Sometimes there is a clunk when it is trying to make up its mind which gear should be selected at low speed.
4/ Apart from the above can't really see much of a difference from the six speed box.
In D its really smooth, you cant really tell the gear changes. Further in S-mode and with sports buttion activated its shifts really fast.
Mine also make the clunk changing gear from second to first. And I have had a gear failure twice. When I putted it in S-mode and decided to manually shift just before it hits the red line. The gearbox shifted to neutral, stopped over and putted in D again.