Simply its great to have the extra level of authentication and its nice to see that the Plugin creator has been creating other similar authentication plugins.
I couldn't figure out how it worked initially. There's no settings associated with it, or anything to indicate what you should do. Eventually it becomes obvious that you have to enable it on a per-user basis. Each user has to log-in and activate it for themselves. It also doesn't give a very useful default title for the description - meaning everyone has to update that.