its really simple for me:
#1 Improved Trackman numbers (i'd be happy improving even just 1 and, assuming the balls going where I'm looking, I don't really care which one) via a way I consistently repeat or know that I can ultimately consistently repeat.
#2 A better understanding on WHY the numbers I improved were an improvement and HOW he got me there.
#3 Affirmation and Motivation! I like to think my instructor believes I'm a good golfer and that I can reach my goals. Not sure why, I just do.
#4 An idea of where we'd like my swing by the next time we work together.
There's only 1 instructor i've worked with that gives me me all 4, 100% of the time. And I generally get a lot more than just those 4.
Before trackman, I'd have said something that improved the plane of my swing on video, to fix any misses I've been struggling with but #3 and #4 would have been the same. The problem there was I could get my swing to look "perfect" with the lines and what not and I still not know where it was going... So I would have been better off just working on my short game. HA.