In detail, what changed:
https://bazaar.launchpad.net/~toykeeper/flashlight-firmware/fsm/changes
Or a more readable version of the changes can be seen with bzr log -v -n0 , or with a history visualizer tool. I normally use the “vis” tool from bzr-gtk, which looks like this.
There have been some improvements and bug fixes since June, but I can’t really say whether it’s worth taking things apart to upgrade or not. It will probably do thermal regulation more safely now, and there’s a hint on hold-from-off to indicate the timing for getting moon mode, but I doubt you’d notice any other changes during regular use on a D4.
The 1.2mA vs 1.4mA thing isn’t due to firmware. It’s probably more related to differences in emitter response time, Vf, and battery voltage.