Originally Posted by HP Man
As long as the stock brakes have the capability to lock the tires (as the M3's brakes do), you will not see shortened braking distance with a BBK for a single stop. Of course, as noted above, for repeated stops where heat dissipation is a problem (such as track driving), then a BBK is definitely worth it. IMO, a BBK is a complete waste of $$$ for street driving. My $0.02.
Exactly. As long as you are capable of engaging ABS then you are using 100% of the tire's ability to slow the car. The only way to reduce stopping distances is to increase overall grip. What a BBK gives you is increased thermal capacity which increases the car's resistance to brake fade, not shorten your braking distance; however, on the street I'd hope you're not making "10 repeated stops from 100 to 30 mph" because that would be pretty reckless and should be saved for the track.
If you want a firmer pedal and improved braking feel then get SS brake lines, better brake fluid and a street-performance brake pad but don't waste your money on a BBK unless you plan on tracking your car.