The over-travel set screw, allows you to reduce the trigger travel after the SA break, there by shorting the reset (overall trigger travel before reset).
The allowable adjustment is different depending on the pistol you have installed it on. In other words some pistols do not have as much over-travel to begin with, while maintaining sear/hammer hook clearance. I have a CZ that benefited greatly and another that benefited very little.
Thus far i prefer the look and feel of the Old 85c trigger. Though i have not personally confirmed it, i believe that the added thickness of the Old 85c trigger is added to the front, there by moving your finger forward slightly. If this is correct, it marginally increases the reach over a New style 85c trigger.