I really like the way you integrated the vbulletin. If you don't mind could you tell a little about how you did it? Did you just modify the templates in vbulletin to make it look like part of your site?
Yes, that's how it is done. You just need to modify vB's header, headerinclude, and footer templates. You then need to create a copy of the Joomla template's CSS so you can adjust (remove and change some entries) so it will work well and look the way you want with vbulletin. Since this is done manually, any changes in Joomla's mainmenu will have to be manually done in the vB template.