It makes a 'measurable' difference (i.e. 400rpm or so) but only speeds up the process slightly. It won't actually give you any more power than what that motor was going to deliver anyway.
All I do now is throw the motor in and run it a few times (after its been tested to see if its a half decent one in the first place) and that's it.
Certainly Cal is correct in that the motor is only part of the equation. Decent high voltage cells are just as important.