I'm now having this problem with Natty on my MacBook Pro 6.2. I tried Mario's cpp tool, which compiles and runs but always reports the brightness as 0.
Like some of the others posts in this thread, my folder /sys/class/backlight is empty:
$sudo ./apple-backlight -n -s 1
valid range: 0-15 (0xf)
setting brightness to: 1
current brightness is now: 0
nvclock reported that my graphics card isn't supported. I installed nvidia-bl-dkms from mactel, but I notice there is no mbp-nvidia-bl-dkms for Natty. Could that be the issue? Any ideas would be great and thanks for restarting the thread!
$find /sys/ |grep backlight