The page mentions improvements but I can't tell from the main readme what is the advantage over the stock firmware, which I found to be quite nice for my personal use.
https://github.com/flipperdevices/flipperzero-firmware/relea...
or more details here:
https://github.com/flipperdevices/flipperzero-firmware/compa...
https://github.com/flipperdevices/flipperzero-firmware/commits/dev/