Took the plunge and installed the update. Ran into a minor snag, but which I eventually recovered from. The idea is NOT to panic.
Here's what happened (skipping through the uneventful stuff). After downloading the update, I connected to the aircraft and initiated the upgrade. Waited a few minutes and then it shows 100% Update Successful. Pressing Finish, it instructed me to restart the aircraft. But then, when I dismissed that pop-up, I heard the controller restart (it made 3 beeps as if it was just turned on) and "Upgrading 20%" on the screen. So I didn't touch the aircraft despite the instruction to restart it and just waited for a few more minutes. The percentage didn't budge beyond 20% and to my dismay, Update Failed appeared.
So I turned off both the aircraft and controller, waited a few seconds, then powered them on. The gimbal went limp (the camera was just dangling there). I restarted the update and this time, it eventually returned with the good news... Update Successful.
Restarted everything again, checked the IMU and compass, then took the bird out for a test flight. The aircraft appears to be behaving normally.
The thing with this all-in-one update is that, it's a single file that simultaneously (or sequentially) updates the controller, aircraft/gimbal, and battery.... not really sure if there's a sequence. Here's what I've observed, if you power-cycle the controller, the aircraft loses WiFi connection to the tablet and it will take several seconds to reacquire. In my case, I am guessing that the controller finished first then it rebooted by itself, cutting the connection to the aircraft, interrupting the aircraft update and got stuck at 20%. The good thing though, it wasn't left in a bad enough state and it still allowed me to retry and finish the operation.
In retrospect, DJI should really work on adding more fail-safes to the update process. I think they made it too easy to mess it up... even if you follow the instructions to the letter.