I usually keep the cookies from fedoraforum.org and my browser is configured to remember my username and password. But either way, it can take a while for the first pages to load. I've tried this on firefox, opera and IE (both Fedora Core and Windoze); it's pretty much the same. Once the pages are cached, navigating with the forward and back buttons is snappy, but any new link and the browser is waiting for the php script to get parsed on the server.
I am also on antionline.com, and their forum is also powered by vBulletin. They have quite a bit more ads embedded in their pages, but the pages render significantly faster than fedoraforum.org.
Oh well, it's not the end of the world, I can live with it.