I just had my PEM replaced by Tesla, and they updated the firmware to 4.6.8.
Interestingly, when I had the car in for its annual service back in April/May of 2015, they did not update the firmware then.
The difference I notice is that the headlights don't automatically turn off when you turn off the car and remove the key. Previously, I leveraged the "feature/bug" to be able to leave my headlight switch ON at all times. Kind of a bummer for my use.