the shader only reacts to the sun light I believe...If we could get ambient light (so they are not so dark) and point lights to show, it would be fantastic...
The only way to use the shader right now is if you want to make a level with extreme contrast...like doom3.
Maybe one of the shader gurus can help out?
(I just remember that this might not be possible yet, until the new lighting system that conitec have forecast is released)