Regardless of your personal philosophy on using a beta OS or not, one thing is clear: YOU SHOULD NOT use beta software on flying machines. I mean, unless you a) want to risk a crash and b) void any warranty / DJI Care Refresh (I don't know for sure, but I would be worried that running a beta OS would render the Refresh void).
Yes, I know that the iOS does not actually fly the AC, and that you can fly without the a controller app at all if you want, but if you are flying with a controller app and the OS gives it invalid data, you risk the controller app crashing the aircraft.
Chris