I have to agree with Ahura, he is right about the text size (which could be bigger), although I think readability has less to do with text size than it does with the clashing color schemes and terribly high contrast. It is far
too high contrast ... white text frames against a black background is very harsh on the eyes and makes focusing difficult and even painful after looking at text for a few minutes. If the forum is to go black, all frames should be black as well, or at least a shade of gray. It's all too too hard on the eyes ... there is too much going on. The light blues and neutral tones of the previous forum were gentler on the eyes. It may also just be me, but there are an awful lot of Google Ads; I honestly don't even remember these on the previous forum, not so much because they weren't there (I'm pretty sure they were) but because it wasn't blatantly obvious and intrusive back then like it is now. These ads are appearing where most would expect to find navigation or margin controls. Is this an intentional psychological aspect of the design, perhaps hoping we'll accidentally click an AdSense entry? I'm sorry, but the placement of these ads is just arguably intrusive.
The forum software itself might be improved, but if this was change just for change's sake then it seems a little premature. I think it could use some revision ... it doesn't have to look exactly like the old forum, but the old forum was better laid out and easier to look at than this. If you want to see a good "dark" color board scheme as a good example, check out HardForum
for some inspiration. That's dark and still easy on the eyes because it basically uses two warm colors on a dark background (red and amber against black and gray). This new forum has both warm (yellow/orange) and cold (green/blue) color schemes coexisting on terribly contrasted white and black backgrounds. This board is "figuratively" wonderful to visit, but "literally" painful to look at ... and deserves better.