You know this is a good plugin - in principal, but it is beset with issues.
First of all the lack of documentation to help people, especially those who may not be tech savvy or familiar with Facebook jargon. This sadly also then goes onto the support - support is a regurgitation of changelogs and full of tech speak and assumptions things have been resolved just because support has answered.
My first issue with this plugin and consequently first call for support saw the support tell me to read the changelog and click the topic to resolved - this is not acceptable as support and also quite telling - there is an assumption that you've been "stoopid" and not read the documentation.
I think FB need to look at this plugin and properly test updates before they go out. They also need to work better with the WordPress repository as comments are now owned by FB and should something go wrong, the client/user looses their comments.
FB, need to also look at their documentation. It claims a simple out of the box set-up but it is anything but.
FB also need to look at their support - I am not saying the person is bad just the way they look at support issues and their subsequent answers and quick resolved ticking are not helping. The assumption that everyone speaks the same tech-speak as them is also not helpful.
I'm giving it a three because as I said in principal its good - things just need looking into.