Taking into consideration site demographics, the bulletin boards could really use some speed enhancements. With the assumption that most users accessing the site overall have raw browsing speeds of 10KB at best, running vBulletin is suicide. First is the fact that it is a full-featured, fancy forum application, but it wasn't made for usage in low-speed localities.
Normally, the apparent and obvious choice for a site like this would be PunBB (demo), but I understand that the userbase here would go for more eye-candy than performance, so a balance of both worlds would be PhpBB (demo). Both are PHP- and MySQL-based, and there should also be converters or migration scripts around.
My main gripe is not with loading pages per se, but with replying to and editing posts - it takes like, forever.