Remember, cars like the M3 stop so quickly becuase of ABS and good brake design. I still don't see the need for multi piston calipers (which are larger and gives less cooling surface to the disc) if the single piston caliper is more than adequate. If you're going to be on the track then I would expect some kind of brake upgrade. The m3 was built to be a very sporty street car, unlike the porsche which is designed to be a road going track car.
It doesn't take a super powerful brake system anymore like it used to (to an extent... don't get me wrong!! Powerful brakes are necessary but not like it used to be). You can lock up the wheels in an instant with those stock brakes, but the ABS prevents that which is why in the end it doesnt really matter.
On my 325is I didn't notice any uneven wear from the front brake pads. Maybe your rotor was warped?
![[:D]](/images/smilies/biggrin.png "Big Grin [:D]")