Comment 91 for bug 954661

To all those wondering about backlight in Precise and Quantal, if you switch your BIOS mode to UEFI, and reinstall Ubuntu in UEFI mode, it will fix the brightness issue. You can use your function keys out of the box, and they will change the brightness accordingly.

The only issue is, with the fresh Precise installation, you will need to update your kernel through the Updater, otherwise your brightness will be stuck on the lowest one. After an update, all issues gone, and you can use your laptop as is :D