Forum Moderators: phranque
I've heard that it can be a resource hog, but I suppose that would depend on the levels of traffic you expect.
I use phpBB2 on my site, and given that it's free (GPL) software, I think it's pretty excellent. I'd highly rate phpBB2, and recommend it to anyone.
Support on the phpbb.com website is very good, much better than that given by many/most commercial companies. I've found one drawback is that you can't splice topics together if you need to, but that's been promised for the next version, and is not a serious issue for me.