As far as readability goes, it strains your eyes after a while because the contrast is too dramatic.

Personally, I think #333 text on #FFF background is a good combination if you still want high contrast text (eg, Facebook).

And I find the #000 straining enough that I use the Firefox extension Stylish in order to customize the font colors on certain websites, like Wikipedia. However, you'd think that a giant text heavy site like that would run some readability tests or something. *sigh*