Wow, this thread is like a combination "Mythbusters" and "General Hospital." Drama plus engineering . . .
I have been time trialing an E36 M3 with stock calipers, OEM Euro E36 M3 floating rotors in the front (same size as US, but 2-piece like the E92's for lighter weight and better heat dissipation) and running stainless steel lines, super blue fluid, and Performance friction race pads (PF 01 front, 97 rears). I removed the dust shield in the front for better cooling. Even running the car hard to its limit on near-slick race tires, the brakes do not fade (except if I let the pad thickness get down to a quarter thickness). I have driven lots of other people's cars and am equally impressed with the power, lack of fade, and longevity of my brakes.
I actually think BMW may have given the 1-series 6-piston brakes more for marketing reasons (to attract the STi/Evo/350Z crowd) than for performance reasons. I believe they use solid rotors on the 135i which are smaller than those used on the 335i's single piston set up. I'd take the single-piston M3 brakes any day.
I think no one denies how good Porsche's brakes are. They have always been known for their brakes. However, with small changes my E36 M3's have been equal to the Porsches I have braked against. I, for one, hope the M3s are up to the task of 10/10ths track work (at least on Toyo R888s or similar R-compounds). I assume it will require a change in brake fluid (minimum) and perhaps some higher temp pads. I will find out fairly soon. I am impressed with the brakes on back roads so far, but that is not much of a test.
Driving sideways: It's not faster, but damn it's more fun!