I just received 5 of these HK SS 18-20a Card Programmable ESCs
which I plan to reflash with SimonK's tgy.hex firmware.
I probably wouldn't have considered it but read about n3m1s1s's problems with these HK SS 18-20a Non Card Programmable ESCs.
It seems that the firmware recently changed and now they release the magic smoke when connected to some flight controllers (not sure what he is using).
Then I read Warthox's recent bad experiences with his favorite Hobbywing ESCs where they recently switched to a SIL chip.
So maybe there is not much of a difference between "good" stock firmware on a HK ESC and SimonK's.
But...I don't really trust what fw version they loaded at the HK factory. Also, I understand that the motors run quieter (less whine) with SimonKs fw and most report more stability after reflashing.