ESC's are all flashed with SimonK firmware.  The one problem I had was that I flashed the wrong firmware on one of them and it started smoking one of the motors.  Now even though it took the new flash, it will not power the motor correctly so I have some troubleshooting to do.  The motor actually tested out fine, but we'll relegate it to the spare, as I don't know if its lifespan has been reduced or not.