With the acpi_osi option in place, it seems like the brightness is reset to the last /known/ level after x seconds of no user input (mousemove, keystroke). Normally wouldn't be a problem, but now that the brightness set by the function keys is done independently of the power daemon (or whatever), this is more than a little irritating. My workaround has been to have a script running in the background (uses xdotool) that moves the cursor by 1px and back every ten seconds - clumsy, but it's a functioning workaround for now.
With the acpi_osi option in place, it seems like the brightness is reset to the last /known/ level after x seconds of no user input (mousemove, keystroke). Normally wouldn't be a problem, but now that the brightness set by the function keys is done independently of the power daemon (or whatever), this is more than a little irritating. My workaround has been to have a script running in the background (uses xdotool) that moves the cursor by 1px and back every ten seconds - clumsy, but it's a functioning workaround for now.