I went to a Bridgestone fitting where the fitter used Trackman. The stats showed a clear difference between the ball I was using and the one recommended. I gained a few yards, but also more consistency. The fitter took the time to explain why. I know there are quite a few sceptics out there about ball fitting, but since it is free, why would you not give it a try?
Two sides to every coin. On the one hand it could be used to see what ball flight is a consequence of your swing. Then again, EVERY ball flight is a consequence of your swing, so the ball used is of little significance. It has been said many times before, unless you only ever hit the ball with one speed and one club, then using Trackman to analyse the stats could be deemed useful. But since in golf this is never the case - and ultimately the majority of shots are played with a putter anyway - it doesn't serve any real purpose, other than telling you what your eyeball can see anyway. Fit a ball around your putter first - worry about the rest of the stuff with your eyeball.