FWIW, I have been driving with the M Perf brakes since taking delivery in Aug. Getting the new brakes installed was an issue and took longer that I would have thought, they had to get tech info from Germancy before the car would "accept" the new brakes - I even had to take it back once in the first week, but since that time no issues and now that the car is broken in with 4k miles, it brakes awesome. Apparently YMMV, with is too bad.
Supposedly, There is only one tech at my dealer who qualified/experienced enough to do the work (or so they tell me). I did talk to the tech who did the work and he did say the install was a bit of a pain, so I am wondering if people's issues are the result of a somewhat botched install.
In any event, I am happy with the choice and I made sure that my tech got a bottle of scotch for his patience and work (which, I might add, as purchased some good will going forward