I just happened to come across this script phpbb2drupal for converting phpbb forums to drupal. At work we currently use drupal, but when I installed it (4.2?), forums weren’t nearly flexible enough so I went with phpBB just to provide forums (with a hack for LDAP authentication). I have been unimpressed with the administration aspects (users, groups, and forum permissions are all over the place) and security vulnerabilities are reported pretty regularly. With Drupal recently releasing version 4.6, I’ll hopefully upgrade as soon as the semester is over.