I always find this a frustrating topic! My pb is 2@38, 34mph. We have a high level skier here (jr worlds and some pro tours) who would choose not to ski at all if the right driver is not here. It really bugs, you can go on you tube and watch numerous videos posted of clinics that Andy Mapple has run and just got one of the people there to drive for him, I have seen him into 39 and not sure but I think 41 with these amateur drivers. I know the driver makes a difference, I have my preferences too and ski better behind certain people. I think this is mainly just being relaxed and trust them. My wife is one of the drivers and by no means is giving me a perfect ride. I just know what she is going to do. The people I won't let drive are either I think they might do something that might hurt me physically or just ruin the set by putting rollers in the course.
I had the opportunity to ride in the boat this year with a pro driver who gave me some great tips. He said he will not move the wheel until the he feels the skier.