I did the update today using my EOS 70D. It was an interesting day to say the least,...luckily I had the BG-E14 battery grip with 2 fully charged batteries in it. I started the update and it was at 98% completed when I had to leave due to an emergency regarding a friend. I got back 7 hours later and it was still at 98%. At this point I called CANON CPS for assistance. He said take the battery tray out to stop the process and then put it back in and check the battery status, one was at 0% and the other was at 23%. Again I pulled the pack out and replaced those batteries with two new fully charged batteries, turned the camera on and checked firmware status, and the update had completed. Apparently on a RARE occasion the display gets "hung up" even though the update function did complete.