Re my 2010 E coupe headlight switch: The rotary knob is illuminated at night, but the ring with the markings for the different switch positions is not. Seems strange to me but my dealer says they are all that way.

 

My 2012 E550 is that way as well. So at night you cannot see the white icons on the ring, only the knob. I also thought that was a bit strange, but that is how it is designed.