It's only when you start migrating your own forums, bumping into trouble, that the enthusiasm subsides and you see the reality.
That things are even better than they look
I'm so glad I made the choice to convert my main forum to xenForo. All the issues I've had, all the problems, the questions, everything, the community was very friendly and welcoming in responding and trying to help me out.
The software itself is very modern, doesn't have any bugs, no security issues, really nothing I can think of that made my experience miss vbulletin or IPB or anything else I've used in the past (edit: mind you I had what was probably one of the most customized vbulletins in the world...)
I also like the approach the xenForo team is taking, trying to make the core forum functionality as best as possible, instead of building multiple addons to expand their portfolio - from all people I know this would be a welcome move on my end, but I am very happy to have a fantastic core forum script first.
I started with 1 license for my main forum, and I now have 4 of them, and still need to buy a few more to convert the rest of my forums.
One last thing, which to me is more important than all the above: xenForo has given back to me something I thought I'd lost: the desire to work with my forums once again.
So, a big thankyou to the xenForo team (I hope sales are going well, we're doing our best here giving you all our money ) and to the community. Both of these parties combined have made this script a wonderful experience to work with.