I actually think that phpBB has more support, plugins, etc. than paid forums. There are more indie developers using free forums, such as phpBB, and thus more extensions.
As for phpBB being "bloated web 2.0 garbage", it's not this
. It's just nicer on the eyes, and still a simple look.
It's up to you, as an admin of course, but personally I can't stand the look of SMF.