I hate light-on-dark text viewing. Humans like myself are diurnal creatures, used to viewing things in the light. Command line interfaces use light-on-dark because back when the first command lines were developed, white was expensive. Remember when computer monitors were all black with green or orange text? It's (obviously) not as easy to read black on flourescent green as it is to read green on black, but at the same time it's easier to read black on white than just about anything on black. White gives the impression of clean emptyness.