Originally Posted by SpecialK 
Are you talking about the focus confirmation indicator? Not sure what you mean about "first guess".
I believe he means a way to keep the AF system from "double checking" the focus -- if you pay careful attention to what it does, it seems to hit the focus point, then do a quick forward/backward step to verify it. This slows down the time to shoot a little and some people would be willing to sacrifice that final step for some improved speed.