More and more of the large forums are now switching to XenForo, some of largest in the UK I have noticed are now using Xen. Why?? Because, support from third party coders is dropping off at a staggering rate, so many people are fed up with the way vBulletin is going and I am not surprised. vB5 is just a mess, whether that will ever improve is another matter, and now vBulletin 4.x is just becoming compromised far to often for people to recommend it.
Products are supposed to improve over time, not become worse.