Out of all the WordPress -> Facebook plugins that are out there, I must say that this one is probably the easiest to setup and use. But don't let that fool you, from the WordPress side of things, it is easy...from the Facebook side...like all Facebook things...it's a bit of a nightmare.
But if you follow the setup instructions step by step by step by step you should get it working with out any hassles.
I would have given this plugin 5 stars, but as a developer, we all know that nothing on the web is ever 100%. But like I said I think this is the best so far.
On the Facebook side:
Just a word of warning for those trying to set up as a Developer on Facebook so you can create the App. This mainly applies to Developers in Australia though as that is where I am located. When signing up as a developer in Facebook, you are required to verify your account via sms. However, the only service providers that support text messaging from Facebook in Australia is Telstra and Optus (and also Virgin as they use Optus). So if you are with any other service provider you will not be able to receive a verification code. I found this out the hard way...so best thing to do would be to find a friend or relative who has Telstra or Optus as a service provider and use their number. Then get them to forward you the verification code.