I'll sign up. I agree about paid forum. I'm on many forums, some huge ones, and I've never heard of one requiring subscription. I'm not saying it's not worth it, but for my own personal cheapness, I can't seem to justify a paid forum at this time in my life. So, I use this one but as soon as a thread hits 100 messages, I'm out. This sucks for me, but like I said, I'm cheap. I can't even afford to be on a snowbike, much less the forum.
I also agree about limiting sub forums though, especially starting out, it will be too diluted otherwise. Wait until the main forum is too high traffic, and then discuss sub forums.