I dislike reading white text on a black background, it blurs on me, even with glasses. Years ago I had a discussion with Mike Reichman of Luminous-Landscape (which has that color scheme). He did not budge on his claim that white on black is easier to read than black on white, apparently dismissing my experience. But I looked it up, and it is real for many people, and it seems to be related to astigmatism of the eye. Funny enough, white on dark blue (like ole time WordPerfect) is no problem.
I have not found a solution to Mike's site apart from just enlarging the text to ridiculous levels. But DPreview.com I just stumbled over one: at the bottom of pages is a "print" link. If I click that and dismiss the printing dialogue, I get a nice white page to read. (I've set the pages in my email program to be light grey, I find this the easiest on the eyes.)
Some people even get headaches from white/black pages.
This page has this statement: "Note: People with astigmatism (aproximately 50% of the population) find it harder to read white text on black than black text on white."