Great vBulletin / MediaWiki integration.
One small issue.
When I try to "Register for your site" via the wiki's Log in / create account - they are the same URL. And I can't seem to create an account that way.
I suggest either
(1) remove the words "create account"
(2) redirect "create account" to forums registration.
Now I do suppose most people are registering from the forums anyway ... but NOT everyone !
Especially as your wiki grows.
Otherwise ... great great job !