I just imported a forum from a old one I have under phpBB2.
Almost everything is ok, don't worry
The access rights gave to a group where not imported (I marked all the possibilities to import). I explain :
When I go to the groups and users right for one specific forum, as well than the "forum moderator" part, this ones are empty, for all my forums. What means this data weren't import.
Don't worry for me, it's not a big deal, I can easily put the right back because I don't have 100 groups.
But just to show you this problem.