It's a very unique traffic source, so where would you go next?
Adwords or elsewhere? Would you judge by type of offers you run on Facebook or the traffic source type?
More interested in lead gen and sweeps but would love to hear some feedback in general!
I think Instagram and Native would be a great addition if you run Facebook with succes. They have kinda the same ad setup and most likely your winning FB images and titles will be succesful on Native too.
For example Pops, display, email marketing and Adwords are a total different sport I think.
Quality wise, adwords or bing compare, properly targeted adwords is even better IMO, but you're right, FB is very specific source, the targeting options they have are unmatched by anyone else.
Native networks, suggested by stickupkid, have massive volume too ... it will take quite some effort to optimize thou. Look up some posts started by stickupkid, he posted several great ones about native lately.