Comment 8 for bug 516354

$ cat /sys/class/dmi/id/product_name
MacBookPro5,3
$ echo 0 | sudo tee /sys/class/backlight/nvidia_backlight/brightness
[sudo] password for myusernamehere: (typed password)
0 (backlight not changed)
$ echo 512 | sudo tee /sys/class/backlight/nvidia_backlight/brightness
512 (backlight not changed)
$ echo 1023 | sudo tee /sys/class/backlight/nvidia_backlight/brightness
1023 (backlight not changed)
$

I don't know if this is relevant, but back on an older version of Ubuntu, the keys weren't working either and I to work around this I had set up two scripts that I had bound to the F1 and F2 keys, and they basically did the same thing: Incremented or decremented the contents of the brightness pseudo-file. However, the file path was /sys/class/backlight/mbp_backlight/brightness, not /sys/class/backlight/nvidia_backlight/brightness. I do not have a /sys/class/backlight/mbp_backlight/brightness file any more now.