[dmlawrence]

Actually, the first number I quoted was just a mental approximation. Here's a more exact number:

Mu changes from .05 to .06 - an increase of 20%.
Force of traction = mu * normal force, so traction also increases by 20%.
Max acceleration = Force of traction / mass, so acceleration also increases by 20%.
Time = sqrt(2 * distance / acceleration), so for a given distance, a 20% increase in acceleration corresponds to 1/sqrt(120%)=91.3%, or an 8.7% decrease in time.

This doesn't seem to match up with the results mentioned above.