We've transitioned all the users to the new forum, or at least sent an email saying the old forum is now defunct and to use the new one.
We're having some very good experiences from a technical perspective. The forum is running on a virtual server and is about four times faster than the previous SOOP forum we were using privately.
Forum permissions are a little tricky, but only because they're so configurable. We've created some private game forums for ongoing campaigns, but for now they're public until we can figure out a streamlined way to do user permissions.