Comparing the two side by side I find readability to be easier on the older site. The newer font seems slightly different, though it could be the contrast of the background colors.
1. Is it possible to display the Username in a more prominent font? Iconography looks fine, but when scrolling and picking out users without icons it would be nice to see a larger font size.
2. Post breaks between the user bar and the post itself helps differentiate the columns. The black bar between posts is a pretty good defining line. Some users seem to have a more prominent break between posts than others. This looks to be very dependent on monitor, I can have it on one screen and see the alternating white bar and slight grey background while on the 2nd monitor it all looks totally white with no difference.
3. I'll say I don't mind the black dead space on the outside of the forum. With wider monitors it takes more eye movement to read from side to side so this is rather refreshing. Paragraphs look like paragraphs and not 24 inch long strings of text.
4. I see some posts display the BBCode, will the new forum parse this eventually? For example
See the 2nd image.
Great improvement, looking forward to seeing how well it handles picture uploads and such.