I lost my entire site to a hacker thanks to V1 of this component on August 1st. The vulnerability is fixed in the new version, but you might want to keep a very close eye out for further problems if you do choose to install this.

Most decent community sites with Joomla will need Community Builder for extended user functionality, and a forum of some kind for discussions. So any forum has to bridge into both CB and Joomla to be useful. There are 3 forums that do this - phpBB, SMF and Joomlaboard. Of these, phpBB doesn't seem that solidly bridged at the moment, and Joomlaboard is far from professional grade despite its use on the CB website. So SMF is what's left.

Which makes it quite lucky that this component is so damn good then. It works fine, has good installation instructions, and a very active support and development community. Reviews from earlier this year don't reflect how much it's improved since then. If you're looking for CB and a forum, this is the way to go.

If you check the tracker, you'll find it's not compatible with Linux, i.e. the vast majority of installs. CB plugins shows it as not installed when this happens. Project appears a bit dead at the moment.