There are a lot of nice things about the new layout, but it feels a bit "crowded" visually to me with not enough to really help people with the hierarchy of information. I think it might help if forum section headers had a slightly different color in the background (something neutral, like a light gray perhaps) and if the "Started by So and So, December 18, 2005 03:03pm" line was lighter or smaller or both. Then the topic headings would have a nice divider and be given some room to breathe and stick out a bit better.
Anyway, all in all very nice. Just a few suggestions that might help with readability!