I am rolling perfect with 1.9.60. I have a W323A which is one of the earlier models with the latest revision of motors. To be honest I have never noticed any difference in firmware upgrading from the fairly early versions all the way up to 1.9.60. This is my second Phantom 3, my first was the early revision and I exchanged it for the new revision for the shell, and more efficient motors.
I feel lucky to have a solid bird, and believe that firmware problems can be the result of a large number of independent factors as far as the hardware modules that are upgraded. When you perform a firmware update so many different subsystems are upgraded.
My usage also bucks many of the norms I read about like calibrating the IMU. I have never done it and do not plan on doing it unless my numbers are out of acceptable range. Many people calibrate the IMU somewhat regularly and I believe this can be problematic. If the numbers are within spec why calibrate when most of us do not have an interference free and perfectly level surface also free of any form of interference to calibrate in.
Call me a rebel, a nut, whatever. I just fly my Phantom and enjoy it without sweating all the firmware paranoia.
I will add one caveat which is I never upgrade firmware until it has been out for a while. This helped me to avoid what I consider to be the single failed firmware version that had battery issues that were serious (I forget the exact rev, it was around 1.5 I think).
DJI has been very responsive releasing regular updates that have improved the P3 which I consider to be most excellent. I believe we may be reaching a period where the P3 will begin to have far fewer updates now that the bird has been thru both a cold and hot season.