Craig,
There probably is some improvement in heat rejection rate with drilled
rotors. It is also true that many racing brake systems heat to very high
temperatures (just watch a night road race and the glowing rotors).
However, airplanes and race cars use brakes very differently. As the
original post said, airplanes typically stop only once before the brakes are
allowed to cool completely. Race cars use the brakes repetitively without
allowing time to completely cool. Thus, cooling ducts and anything else you can
do to get rid of even a little heat between applications is important in a road
race car. If you only have to stop once, heat rejection will have much less
benefit because the braking event will end shortly after the brakes have become
hot.
The main benefit of holes or slots is to allow the gasses evolved from the
hot pads an escape path so that the pad stays in contact with the rotor. If you
are experiencing brake fade, this may help quite a bit. If the brakes continue
to work well from touchdown to stop without slots/holes, little will be gained
from adding them.
Rob