There are a multitude of reasons why the brightness won't work on the Macbook.
do you see any backlight device under /sys/class/backlight?
if there is more than one folder there it possible that the backlight utility is trying to change the backligt on the improper device. This is the Case with the Macbook Pro 15" 8.2 model.
If there is only one. device. You can try setting backlight manually just to see if it works. by typing:
cat max_brightness | sudo tee -a > brightness
this will read the value of the file max_brightness and set that value to the current brightness.
If there is no backlight device. You don't have a proper backlight module installed.
it should be called apple_bl , or nvidia_bl,
try to load them manually using modprobe modulename , and verifying if any device pops up in the folder.