XDForum, another Wordpress forum plug-in, stopped development a few months ago.
For anyone considering converting their XDForum to BBPress, I've posted detailed instructions for converting XDForum tables to BBPress tables on my site. The instructions include a method for tagging your existing content.
I looked for something like this a few months ago and couldn't find it. Hopefully, someone will find this useful. The result of the conversion can be viewed here...