Originally Posted by lettuceman44
... However on the nook you can completely turn the light off. ...
You can turn the light off on the Paperwhite too -- just not with the slider.
Using a launcher of root shell, the commands to read or change the screen brightness (including completely off) are shown here:
The screen brightness values are 0 to 255, but the slider only goes form 1 to 254. I am not sure if that was by design, or a coding error in the firmware.