As others have said, it doesn't really restart the browser. Just closes the windows and reopens them.

The only reason I'm looking a plugin is because the default Firefox behavior is broken. In the best case scenario, I can exit Firefox. And then after re-opening it, have to immediately restore previous session from history. If I exit the browser twice in succession, my "previous" session is gone.

This plugin would have been great if it would have actually restarted the browser. But it doesn't. Not without some additional paid application.