Switching a huge forum to an unproven platform is too large a risk. Starting a new website/community on Xenforo is intriguing, but what happens if the site takes off and I find Xenforo is not a good match? I'm probably stuck, because the demand for Xenforo to vBulletin conversions will be close to non-existent.
I'd like to see the Xenforo Team create a way to easily export Xenforo sites to vBulletin and other popular forum softwares. It would GREATLY reduce the risk of switching/testing, and send a fantastic message that, "we're so confident in our product, we've made it ridiculously easy to switch back to our competitors should you decide."
With this type of exporting feature, I feel like I would have to try Xenforo. But without it? For myself and many others it may prove too risky.
Fingers crossed. Will watch this thread closely.