One of the biggest challenges we faced while making this app was to deal with the new app review process of Facebook developers. Or at least that was what we thought before send our submission, because all of the comments of angry developers saying that Facebook delayed that process up to 5 months.
The reality is that the process was very quick for us (took us a couple days for each submission), and the Facebook team was really helpful with the feedback.
So when our app got approved by Facebook we knew that, since that moment, everything depend on us.