My testbed frame is a basic DJI F450 frame with the DJI motors and 30amp opto ESCs. Its worked fine with a number of different flight controller boards on it, currently has a Multiwii Mega, but the high pitched whine from the motors was really annoying. To fix that problem I swapped the DJI ESCs for a set of old Atmel based Turnigy Plush reflashed with SimonK firmware, big improvement all around.
Yesterday I was at the local electronics supermarket and picked up an Arduino Uno so I could also reflash Silabs based ESCs. Last evening I opened up the DJI Opto to see exactly what was in there and found the FET setup to be an exact match to the current Turnigy Plush 25amp so went for it and reflashed the DJI with BLHeli 9.4 firmware. This morning during my coffee break I went out and flew an entire pack in gusty wind using the newly reflashed DJI 30amp Optos with the rest of the setup exactly the same as I was flying it on the reflashed Turnigys. The annoying whine is gone and it flys great now, as good or better than it did with the Turnigys. I know one flight doesn't prove much of anything but it flys smooth and seems less bothered by gusty wind now with the big plus being there are a lot of configurable options available with the BLHeli firmware. When I did the reflash I soldered the end of a servo cable in place and ran it out under the new shrink wrap so all I need do is connect it to the Uno and run the BLHeli tool to update firmware and change the config, much easier to make changes than with the old Atmel based ESCs!
You can pickup an Arduino Uno board for cheap $ and the software is open source and very easy to use, I would recommend anyone not entirely satisfied with the stock DJI 30 amp ESCs to give it a try. Next I'm going to open up the set of DJI 18amp ESCs I have and see if there's a version of BLHeli firmware that will work on those as well.
Everything you need to know can be found here... http://www.olliw.eu/2012/owsilprog-tutorials/ make sure to click on the English button at the top right corner unless you're fluent in German.