bbPress did not work well for me and is a bear to integrate into WordPress. I tried a few other forum plugins that failed miserably. I don’t want to have a forum separate from my blogs and pages, so I did not even try some of the other choices.
It occurred to me that WordPress comments already have the structure for threaded discussion. I just need a way of putting comments on a page in such a way that it looks like a forum.
I am thinking about a plugin that will replace a page with a forum of comments. I can use the comments meta data for keeping track of forum topics and nest threads under these topics. I would have to tie it to a page, but disable comments so that the normal comments would not appear. I would then have threaded comments not attached to any displayed page.
How I would also integrate custom styling or template pages would be the next question.