Re: bbpress v. other forum software
15 subforums is insane overkill in my opinion. What you need is a Family and Friends forum, a Plugins and Themes forum, and a Other forum. I’m sure that people will be able to cope with seeing Themes threads if they only want Plugins. Unless your forum is so active that, say, you get thirty threads a day in each forum, there’s just no point breaking it up more.
The best thing is, if you lump the forums together then you’ll have way more people seeing each thread, hopefully meaning that you get way more people contributing – not just the few specialists.
Almost every forum I’ve ever seen suffers from overcategorisation, and a a few to sometimes even most of the subforums just lie there unused. What’s the point in that? Get those peoples together.