i got my bbk last year after i warped my stock breaks at Watkins Glen. i had 15 trackdays last year and the breaks held up great. Now they are finally developing a little shoulder on the rotors, but still they are nowhere near at the end of their life. In that time i went through 2 set of front pads.
I spent the last two days at the glen again and finally got a chance to track with another fellow enthusiast also with an M3.
on the front and back straighaway i could outbrake him with at least 100 feet every time.
this upgrade was the most expensive on my car, but it was well worth the money. Btw they are the 380mm 6 piston brembos upfront and 355mm 4 piston in the back.