That solution works for me too.
I have Ubuntu 11.10 and Laptop HP PAVILION DV6
Too make things easier I created a script:
echo current_brightness = $current_brightness
if [ "$1" = "+" ]
new_brightness=`expr $current_brightness + $steep`
if [ "$1" = "-" ]
new_brightness=`expr $current_brightness - $steep`
echo new_brightness = $new_brightness
echo $new_brightness | tee $brightness_file
One drawback here you have to open brightness_file for write to anyone:
sudo chmod 666 brightness_file
Then put the script in a file. For example change_brightness.sh
and you can change brightness with commands
To make even better you can allocate shortcuts on the same f2 f3 keys.