I have four batteries, only one is stock.
I have two O'feelys, one is 5400 mah and the other is 6000 mah. The 5400 I haven't even broken in yet, the 6000 is my favorite battery of the four. It has good flight time and the cells are perfectly balanced. It works perfectly with the newest firmware. The LCD readout is completely awesome and you can see everything you need to know and more right there in the field and it's very bright.
I also have a MAXTOMARS 5400 which is my least favorite battery. It hasn't given me any problems, but the LEDS are so dim I can't see them in daylight and the cell's voltages are further apart than I'd like... like 60 mv. Also when I look in the asst software, the total mAh is less than my stock battery which is odd since it's "designed" to be more.
But I've had no issues with any of my non-dji batteries. They all work with the firmware and they all function well.