I was a vBulletin customer for almost ten years before I switched (switched from a heavily modified version of vBulletin 3.8.7) over to IP.Board less than a year ago. At first I hated IPB. Everything costs money. A simple mod that was free on vBulletin costed money on IPB. I also felt that it was way easier to learn vBulletin than it was to learn IPB. Now that I finally got my mind wrapped around IPB (it took nearly six months to do so) and what it is capable of I absolutely love it.
I would never ever consider vBulletin or any other forum platform again no matter they put out. I just think that at the moment, IP.Board has a better foundation than any other platform out there.
My forum has just under 40,000 topics and 650,000 posts.