I'm a new XenForo user. I recently found your post (http://xenforo.com/community/threads/is-vbulletin-4-a-community-killer.29293/) here in the forums.
I (was) an avid vBulletin user myself. I've been with them since 2006.
Version 4 killed my forum. - I'm now updating everything to Xenforo and won't look back.
Just thought I'd say Hi, since it sounds like you're in the same boat :)