A lot of things changed/added on official RB git compared to the latest build posted here. Looks like most of the performance patches has been added in the official repository plus the code has been re-arranged to make it clean. Further enhancements should be continued from there.
As for the backlight/sleep, my build also prevents DX90 from going to sleep and only turns off the backlight. I found that when DX90 goes to sleep it is prone to crackling noise. There is no battery life hit doing this from my test. It shows the backlight consumes more energy than the rest of the system.