It's a mess and at this point I probably won't ever touch.
Made the mistake of updating by board to 4.0 right when it went gold and that turned out to be a huge headache. Honestly would like to see them still support VB 4 as there's a lot of nice things they could still do with it.
IDK....the fact that they fix over 150 bugs with each release and then 150 more pop up is scary. Plus there's no way to know how it will function on a big board and still there's no infraction and paid sub system in place.
I don't like vBulletin 5. I don't think I'll upgrade my board any time soon and if by the end of the year there's not a massive turnaround, I may convert my forum to XenForo, considering vB4 seems abandoned already.