Completed my first Firmware update for the the MP since receiving it last Friday. I used the battery that was @ 100%, remote control was @ 60%, iPhone 6+ was @ 79%. FW took about 25 minutes to complete. Updated over Wi-Fi at home. Like others had reported, the update hung up at 83% for a bit before completing the update. I restarted the MP, RC and App afterwards, and DJI 4.0 app came up with an inconsistent software/firmware? (Sorry, can't recall exactly) I assumed it was the battery and continued to update that as well. I am waiting for the other two batteries to get to 100% before checking those for updates. So far so good. Loving my Mavic!
EDIT: after checking the other batteries, I did not receive the inconsistent firmware/software message? Not quite sure what was inconsistent, but I don't believe this had anything to do with battery. Everything appears to be good