I enabled "Use Facebook for comments" and "Override Wordpress Discussion Settings" options but couldn't get FB comments to show up in the comments section of my posts. The regular stock Wordpress comments do appear though...
I also made sure I don't have Facebook Comments or any other 3rd party FB commenting plugin installed to prevent conflicts.
I also tried adding:
In the footers template of my theme (I use a Woo Theme) and added "ultimate_fb_comments" to the custom hook input box and still no go.