Comment 22 for bug 341230

Just a note on the "brightness not changing" bug: upon discussion with Julien Blache, the 'pommed' developer (the program to manage the special keys as well as some other sensors in apple hardware using GNU/Linux) it was concluded that this as a bug specific to the NVidia drivers:
http://lists.alioth.debian.org/pipermail/pommed-devel/2009-May/000051.html
http://lists.alioth.debian.org/pipermail/pommed-devel/2009-May/000055.html

As a workaround for the brightness problem: install pommed, and try switching to a text terminal with Fn+CTRL+ALT+F1, then adjust the brightness. Press Fn+CTRL+ALT+F7 (F6 through F9 depending on your distro) to go back to the graphics terminal.

If you find out it's eating your CPU let me know, I just realised I'm running my own patched version and not the one in the debian repos.