I can read!!

Experts have long held the opinion that serif fonts improve readability for text while non-serif fonts are best on back-lit mediums, and subsequently that serif is best for black on light while non-serif best for light on black.
Neither of these widely accepted opinions have held up to proper studies however, and the perceived inappropriateness of serif for any particular medium turns out to frequently be a symptom of other issues such as bad contrast or color/contrast bleed (esp. specific to certain display types or LCD matrices). In similar fashion, there has been no study able to successfully identify advantages for serif fonts (i.e. flow of text, ease of following the line) not gained from good kerning, letter spacing, and line spacing. In other words, the whole point of using a serif font anywhere for any reason still stands largely unproven, except as a means of compensating for other typographical flaws.
People who have spent a lot of time here with their eyes heavily adjusted to the weak/soft white on black are going to find this change harsh. Still having a lot of black background actually makes it worse, as our eyes are still being subjected to very inconsistent back light. I number among the people who
hate black on endless fields of glaring white. My desktop theme is rife with muted greys, consoles using large-font grey on black, and only soft splashes of color. On a backlit display, white is just way too bright for anything. But the white on black was even worse, especially for those of us who spend a lot of time on normal sites as well. The white text was barely legible. Light text on dark background always needs to be thick/bold to appear solid and distinct. The font needed to be bolder, or darker (light grey) or anything but what it was.
Adjusting to a new theme will take a while for the hard-core visitors, but they will adjust. And for everyone else the forums will appear more friendly and inviting. If you're one of the people adjusting, or if you have a hard time coping with bright displays, do what I do: put a white fluorescent lamp behind your monitor. This will help a lot to reduce the perceived brightness of white or light-colored materials, without compromising color or contrast. The real issue our eyes have with bright displays isn't the brightness itself (which is still
way less than our eyes absorb when we're outside). It is with the harsh inconsistencies in ambiance. The problem is that we have only one pupil per eye and can't control the range of brightness contrast we perceive. This is also why the site will be even easier on the eyes if the rest of the black background is abolished. I assume from some of the color artifacts I still see that this is an ongoing process.
As for those of you who's posts' readability was compromised by the
color change, I can't cackle hard enough. That's what you get for
screwing with readability in the first place. Your posts were always an
eyesore, except now you can see it too.