Can't get any simpler than this!
No options for dimming - it seems to dim 50% from your currently set level. Also gives a slight bluish tint to the window.
If,like me, you have your display set at full brightness (MBP), your desktop will still be easily readable when dimmed, therefore it would be helpful if there was a slider to allow adjustable dimming.
Working in OS X 10.7.5 Intel