Right now, Rockbox doesn't turn off the backlight when shutting down. After the LCD is shutdown or cleared, the screen is white. In the dark, this sudden increase in brightness can be unplesant, especially when using a dark theme like Cabbie 2.0.
I vaguely recall that this is done to show that Rockbox shuts down properly. When the backlight shuts off, you know the shutdown sequence isn't hanging and power has actually been shut off. That bright white screen also helps show that the LCD has been shut off properly.
Can the backlight at least be turned off on targets which shut down reliably? My 5G iPod never failed to shut down properly in normal use.