For all interested:
P4P and remote controller updated to most recent firmware.
Tested with:
iPhone 7 AND iPad Air 2 (WiFi and Cellular) updated to iOS 10.3.1
DJI GO 4 version 4.0.7 running on both devices

P4P updated using DJI Assistant v1.1.0-2 on Macbook Pro.
Controller updated through DJI GO 4

After updates, an IMU calibration and gimbal auto calibration was performed.

Test conditions were not ideal because there was heavy foliage and trees between the home point and the aircraft after ~120 lateral feet away.
The controller was set to auto channel on 2.4GHz, and the aircraft flown at 200ft altitude the entire time.
Video signal began to degrade at 3050 ft away (~940 m) and was not usuable at 4987 ft (~1534 m)
RTH due to loss of controller signal occurred at 5840 ft (~1800 m)

Verdict: Most recent firmware and iOS version run WELL --> SAFE TO UPDATE!

Thanks for the feedback. You saved me from opening another thread.

Same here but NO NEED to do IMU and GIMBAL CALIBRATION because I was NOT asked to do that by the AC. So don't do unnecessary IMU and GIMBAL CALIBRATION.

I updated mine using GO4 app for both RC and AC. I flew using 4 batteries. LOS up to 26000' with no issues video or signal.

Have fun!

Thanks, what about the tilted horizon? (to windy to test it myself)

Updated both P4p and RC.. After 15 mins flight Looks good without any issues.  Last time when I flew it had significant issues with recording at 4K 60p. Video freezed every 5-6 seconds. I am not sure if this problems is fixed though. Have to download footage first.

Anyone updated on a samsung s7?

SM-17 Posted at 2017-4-15 20:55
Thanks, what about the tilted horizon? (to windy to test it myself)

Horizon was straight. But I did perform a gimbal cal.  I have found that allowing the aircraft to startup and initialize on a flat surface (within reason) solves my gimbal tilt problem. If the aircraft is noticeably leaning during IMU initialization I usually end up with a tilted horizon. I am unsure if these are related, but I never have problems if I am aware of that effect.

dronist Posted at 2017-4-15 19:52
Same here but NO NEED to do IMU and GIMBAL CALIBRATION because I was NOT asked to do that by the AC. So don't do unnecessary IMU and GIMBAL CALIBRATION.

I updated mine using GO4 app for both RC and AC. I flew using 4 batteries. LOS up to 26000' with no issues video or signal.

My IMU gyros were in the yellow prior to and after the update. I calibrated to get them back in the green and the aircraft is noticeably more stable while hovering.  If the IMU is on the edge of needing a calibration, I prefer to move it back to the center.