Wow, there's some great wisdom in these last few posts.
Let me add my 2 cents. Much of the discussion has been that when MDM intervenes that it's some sort of problem (i.e. the car is interfering) or that it's always slowing you down. What I've found that if you have MDM intervening then try a different line or change your throttle input and see if this makes a difference. One month ago, at a BMW Perf Center track event at CMP, I noticed MDM coming on, I couldn't feel it but the light was blinking, in the middle of a pretty fast 90-100 mph corner (noticed that 2 or 3 times). Next time around I adjusted my line a bit, kept same throttle input and presto, gained another 3 mph or so on corner exit and no blinking MDM activation.
So sometimes it really takes subtle adjustments it takes to stop the MDM from activating. I've also found that sometimes just being a little bit slower on applying the throttle on corner exit can make the difference between MDM coming on or not. Keep in mind if you're really egregious then the system is also going to cut power if the stability control doesn't feel it's done enough.
There are exceptions and for autocross, particularly if it's a tight course, then it's DSC off.