The conventional wisdom for social games is that most users would prefer to use their Facebook identities over the alternatives, even on a iOS mobile device.
Since we had already used Apple Game Center for achievements on our prior Bocce Game, we decided to allow users to use their Game Center identities (in addition to Facebook and Guest) in Playscreen Poker.
The very interesting thing is that we are seeing nearly four times the number of Game Center 'registrations' as FaceBook 'registrations'. The two leading games in this category (Zynga Poker and Texas Poker .. Pokerist) do not support Game Center, so that's a pleasent surprise.
Supporting both platforms (and a no-registration Guest sign-on) created some compexities as achievements and leaderboards had to span both systems.
We expected a fraction of the users to sign-up with Game Center but instead saw the results above.
This may account for the popularity of the title, as it has been ranked well in the Casino and Card game catagoties. It also speaks well of Game Center as a identity system for social gaming.