Do any of you use tools to analyse the contrast and colours of your pages?
GrayBit.com for contrast, though it doesn't load everything on the page... I tested Paul O'B's page with it and the fixed sidebar never showed up.
Vischeck.com for testing 3 types of colourblindness.
Seems like it's quite the consensus in this thread, but if you look at the top sites on the internet, such as YouTube, Yahoo, Facebook and of course Google itself, they all use black on white.
I can't stand white (or light) text on dark background (on screens, anyway). My eyes go all funny and I can't see properly for about 5 minutes afterwards. So I avoid sites that use that horrible technique.
Man, you'd hate being a Unix sysadmin : )