Here are some details on the move from Disqus to Facebook we did on Techzim some two weeks ago: http://www.techzim.co.zw/2012/01/our-experience-migrating-from-disqus-to-facebook-comments/
The Facebook comments system has mostly been a pain, especially admin wise. We’re likely to go back to Disqus at the end of the month. Which will just make the anonymous jackasses happy. They’ll celebrate their victory by trolling even more.