You should have light and dark.
That way people can choose. But make your default one a light one as majority of the users on my forum prefer it light.
Honestly it really matters on both the genre of forum and of course personal preference. Personally I don't mind either as long as the colour balance is right, its easy to navigate and the text is easy to read. 😉
I'm not a major fan of them either, particularly on default skins. (I may sound hypocritical by having a dark skin as the default at my forum, but that's because I'm fixing up the other ones).
However, you do get the occasional 'nice' dark skin. There's always exceptions. But generally speaking, I don't really like them.