We currently use Invision Power Board (IPB) for our forum software. Its been great, but its also been a headache for us since we’d rather focus on developing software than maintaining it.
One thing that’s kept us from moving from IPB is that we have tens of thousands of user registrations and I’m not keen on migrating all that data to a new forum software. However, I’m at a point where we’ve had enough security vulnerabilities occur directly from the forum software (sometimes due to my own lack of updating – but partially because I didn’t even know there was an update) that I am considering moving to a new piece of Forum Software – specifically one that integrates with the rest of our website system better.
This would mean that people would need to re-register on the new software, and potentially old topics would be lost once I disable the old software. I don’t think that’s a horrible thing, but if you think it is let us know.