It's really easy and just assume you are going to NOT be one of the people that have issues. Mine has worked pretty flawlessly. Follow this video and you should be good. Listen for the D-D-D-D sounds carefully.
It's simplistic if it's going to work. My quick and dirty is this.
1. Use the Micro SD card they sent you with your Inspire 1 into a laptop and format it there. Then only copy the .bin file to it. Make sure there are no DCIM directories or any thing like that.
2. Make sure one or the other is OFF when flashing the firmware. i.e. Flashing the firmware on the Inspire, make sure the Controller is OFF. Flashing the Controller, make sure the Inspire is OFF. Also, no matter what, listen closely to the D-D-D-D sounds. I turn off all audio white noise to ensure I am hearing what the process is doing.
3. Wait maximum times. I know it's hard, but mine hung for 15 minutes and then finally completed. It was so temping to hit power off...but working in IT I can tell you firmware updates are the most crucial to NOT interrupt. This is when it's writing updates to the ROM's on the board and is essentially writing new code to your device. So when in doubt, go relax for a bit and then power off only after it's exceeded the time or given you the failure message. Same goes for the RC.
4. Calibrate the IMU (it's located under Sensors) after every update. Calibrate the compass before every flight.
Update craft first, including all batteries for this FW update with controller off, then controller via the app with craft off (must be connected to wifi). Also, before doing all that, make sure you have the latest version of the app before starting FW update.
Inspire 1 V2.0 just arrived today... already unboxed... battery seems to be charging ok (fingers crossed). Picked up an iPad Mini 4 as well... in the process of setting it up at the moment. Then I'll need to download the DJI go app...etc...
Wish me luck...hahaha. I'm excited...!
I'll check back in a few minutes just in case anyone has any advise....