I'm running the latest 1.6 on an old motor type and a new motor type P3P. I haven't had any significant issue, other that one time I had a compass error during flight. I had 140 flights before that happened, I had never seen that happen before during flight. This was about my 8th flight after upgrading to 1.6 on my old motor P3P. I had 2 previous flights there in the previous 2hrs, I had no compass problems. Then all of a sudden 30 seconds into my 3rd flight about 300' away I get the compass error. It automatically went into ATTI mode, so I brought the craft back and landed. I recalibrated the compass and haven't seen the issue since. It was likely an anomaly with the area somehow, even though it was at the beach, far away from anything metal.
If you have 1.3.2 you might want to stay right there. You won't have the waypoints or POI support in the GO app, as that support was released in 1.4. However I think you can get that support from Litchi or Autopilot apps. You'd have to check with those vendors to confirm compatibility with 1.3.2. There is an major RTH issue with Autopilot in 1.6, but not sure if it's in 1.3.2, you'd have to check.
1.4 introduced a drifting anomaly in some craft. I didn't notice it very much, but others did. I have a friend flying 1.4 and I see no drifting issue on his old motor P3P when I fly with him. 1.5 was supposed for fix the drift, and it did, but introduced a fatal flaw that falsely triggers battery protection, sometimes turning off all power mid-flight. 1.6 fixed that, but they also included a governor in the battery to prevent full throttle accelerations when the battery gets low. I personally think that was the wrong approach. There were better ways to solve the problem IMHO.
