Since moving to vB I had nothing but trouble. I bought my license less than a month before they released 4 and when I was reading up on it all they kept repeating was that 4 was better and 3 wouldn't be supported for very long (this was not their exact words but instead a feeling that they conveyed heavily). So I also bought v4. In the space of 2 months I bought it twice with blogs for the same site.
Then came their CMS issues. Holy freaking moly. Folks, I'm not kidding when I say I'd have given up my board were it not for my Tech Admin, who basically re-wrote the front page to suit us and then did a total overhaul of the styles. It finally looked great. Of course, that was 4.0 gold release. Then came 4.0.1 which broke everything. Oh, and 4.0.2 that broke everything she had fixed in 4.0.1...Keep that up until 4.0.6 and you have an idea of what we (and probably some of you) went through. Upgrades took HOURS and we had to shut down during that time. Each upgrade brought in errors that needed to be hunted down one by one.
Then XF came out & we started taking a look at it. At the time vB was at 4.0.6 and we didn't bother going to 4.0.7. When Beta1 was released we installed it on the first day and tested. Beta 2 came out, our test site got a facelift and the upgrade was flawless. Continue that until she announced she was having to leave as the Tech Admin. That put me in a quandary. Stay with a stable vB site or make the switch live? Okay, not much of a quandary. We shut the board down for LESS THAN 1/2 HOUR and we were switched. The only thing that didn't work were the redirects, but that's because we had our directory structure set up all weird. I still have it weird but am going to wait for 6 months or so to fix it.
So there you have it. My site is now on XF and humming along nicely. We've had a few issues here and there with things like permissions (which still confound me on a regular basis even though I thought I had them down) and small things like that, but nothing show stopping.
So I gave away my vB license. Good riddance to ya.