Just installed Xubuntu 9.10 (Karmic Koala) on my Sony Vaio Laptop (VGN-FS215Z) and the thing that REALLY started to bug me (besides the pesky tap-to-click function) was that there seemed to be no way to control the backlight brightness!
Gnome-Power-Manager has a brightness slider alright but for some reason the brightness slider makes not a blind bit of difference to the brightness – Stupid or what?
I was just about to give up when I thought there must be some other utility, and it seems there is in the name of kpowersave.
This handy utility not only has a slider that works, it even has other useful functions.
I did note that it does not seem to “autostart” on login, even with the box ticked, so I simply added “kpowersave” to the startup programmes. (Main Xfce menu > Settings > Session and Startup)