I know it is beta, and I certainly know what I'm doing, and willing to go for it.
When vB4 came to be, I downloaded the very first beta versions. I was, to say the least, irritated. I just installed the thing and I would find a bug, then another bug, then another bug, then another bug. I though "Hell, if I, as a single user, one person, finds these many problems, it is NOT usable". I was angry.
I waited .. .and waited .. and waited. Till this date I have a license and have not installed it.
Then, tired, I bought IPB. It looked nice. However, I could not get past the importer. I kept getting error after error, for any amount of random reasons. I went to the forum, and, sure enough, they answered very politely and were very helpful. But that didn't solve my import problem. After 2 weeks of tweaking the IPB code myself, I gave up. IPB was not ready to deal with my modified and busy vB board.
Then I found out about XF, and since 3 weeks ago, I have been migrating my forum. Today, is the day I finally open it to the public. It is different, but here is the thing, it is "new and exciting", so it is "different good". People love the news feed, the stream of activity and the "Like" everywhere. Logging in with Facebook is a plus.
But here is the real thing for me: as I was translating the forum to Spanish, I had no issues. When I was translating vb4 I had to run to the forum and post "People, you cannot have words as phrases, that is PROBLEM SOLVED since version 2, PLEASE". With XF, I see where all the experience went. Everything is smooth.
I am still not ready to migrate my main, 8 million posts website (I am not there yet), but this was a step. Migrating my spin-off forum with 400k was the test. Now, live, I'll see how the load goes, and what the users think. If they are at least 1 percent as excited and optimistic as I am, this migration is going to be a success.