Hey Guys - just thought I would add my $0.02 worth. I had my second track day in the M yestersday. The first day I ran MDM on all day as I wanted to get used to the car.
Yesterday morning I did the first two runs in MDM mode to get the track layout down (never tracked there before). After that I turned the DSC OFF for the rest of the day. I would say that I learned more about my car in the next two sessions than I had previous. It teaches you to be alot smoother and in turn makes you much faster. I feel like I am driving the car at about 8/10ths now and will build on that the next track day.
I spent a session in the passanger seat of Gearhead's M who drives at about 12/10ths so I know there is lots of room for improvement for me. He has some serious experience and skills!
All in all DSC OFF (with some self discipline) is the best way to track and learn your car IMO.