We also got better results from Facebook Ads than from AdSense. Something that we found is that we got better results if we changed the image on the Ad periodic

We also got better results from Facebook Ads than from AdSense. Something that we found is that we got better results if we changed the image on the Ad periodically and if we stopped for a while our campaigns. We track the user by source, so we can check if the FB users are more or less active than users from other Ad networks or from users that come from organic search, and so far we have not observed a significant bias. We are paying a few cents for each user registration (not click). No other Ad network comes close to these numbers for our site. Our budget is of some (single digit) thousands dollars per month, and we have been running these Ads for a few months.