I just wanted to post an update for anyone thinking of using this plugin. There has been a problem with the logout functionality. However, the problem only occurred between specific versions of Joomla and JFusion (Joomla 1.5.23 and JFusion 1.5.6). There is now a stable version of JFusion 1.6 that works both with Joomla 1.5 and Joomla 1.6. If you are having problems, please upgrade your Joomla install to JFusion 1.6 with the download from here
http://www.jfusion.org/.
This plugin along with JFusion 1.6 and XenForo 1.1 work fine with Joomla 1.5 and Joomla 1.6. This should also work with Joomla 1.7, but is untested. Over the next few days, I'll be testing with Joomla 1.7 to confirm that everything is still working and will post an update here once I have everything working.