Re: phpBB -> bbPress and WordPress together
One thing you may run into is conflicting user IDs between phpbb users and existing wordpress/bbpress users. If so, you can change the user IDs in phpbb before you import it by using this mod:
http://www.phpbb.com/phpBB/viewtopic.php?t=388155&sid=3d5e8f776a7086b6fec64c3e80c7cbca
By changing the user IDs in phpbb to 99991, 99992, and so on, so they don’t conflict when they come over.