Hi. The 3 commands that you asked me to try did not adjust the brightness so I've run the commands to report on the video card. This is the output;

01:00.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI Thames [Radeon 7500M/7600M Series] [1002:6841] (prog-if 00 [VGA controller])
Subsystem: Sony Corporation Device [104d:90ac]
Flags: bus master, fast devsel, latency 0, IRQ 45
Memory at b0000000 (64-bit, prefetchable) [size=256M]
Memory at c4000000 (64-bit, non-prefetchable) [size=128K]
I/O ports at 5000 [size=256]
Expansion ROM at c4040000 [disabled] [size=128K]
Capabilities: [50] Power Management version 3
Capabilities: [58] Express Legacy Endpoint, MSI 00
Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
Capabilities: [150] Advanced Error Reporting
Kernel driver in use: radeon

I don't know if it's relevant but when I was running 12.04 LTS the brightness control worked just fine, but I was using the proprietary AMD drivers (fglrx). I can't test this theory in 12.10, because the proprietary driver is not supported by the new version of X-server and consequently Unity does not run.

Regards, Dave.