I like dark as it is easy to read and easy to tell where I am from the other forums I lurk on. While I find it more attractive on dark I am sure that is just a matter of personal taste. The only problem with dark is when someone elects to use a font colours other than standard as it may conflict with black. The unfortunately thing is if this happens I don't read that post and that can be a shame if it is of importance.
Agree that font colours can certainly be an issue with the dark background. Also, the anit-aliasing on all of the icons and the tabs are configured for a white background and don't look good on the dark.