The installation is like most plugins, no problem. But one point is left:
In the readme I see:
Place '<?php if (function_exists("wp2bb")) wp2bb(); ?>' in your templates
Which template, the wordpress or phpBB3? Which file in the template directory? Where in that file? In all intallation readmes I ever read when a string is to be inserted somewhere the readme give something like "in file /blah/blub/blob.php insert this string before ....." - not here. It may be an improvement to add this in the readme, makes it easier for such dumb fellows like me.