I think it's much more readable with white on black than black on white. But of course if you disagree, which is fine -- some people do -- you can use readability, as in mbrubeck's post.
I'm not quite sure why some people really like black/white while others like white/black. Maybe it's something psychological, or maybe it's just room lighting.
I find that, while I like white-on-dark, I tend to require a larger font to comfortably read it than I do dark-on-white.
On the article's page, when I knock the browser "zoom" feature up one notch from default, it's like the entire page magically becomes this wonderful, easy-to-read document.
It may be because I'm on a 1920x1200 display on a 17" laptop screen, but at any rate, I would consider a small upward bump in font size. I wouldn't have brought it up myself, since as I noted above, I can do it myself in my browser with a quick hold of Ctrl and a flick of the mouse wheel. But since the topic came up, I thought I'd throw that in.
