How dark I write really depends on what I'm writing.  I have a few humor pieces which are "light," some horror pieces which are totally dark.  Most of what I write though has shades of both, because I try even in fantasy to make sure that there is a certain amount of realism, and life is both light and dark. 

For example, Jim has things happen to Harry that are VERY dark, but the humor could be considered to "lighten things up."  I mean, how can you not consider "Bolshevik Muppet" a lightening force in that particular scene.

But overall, I'm probably on the darker end of the spectrum.