Apple has finally integrated Facebook into iOS 6. The functionality is similar to that of the native Twitter integration your use to seeing. You can install and login to facebook through the settings app.
Facebook is integrated into Game Center, Safari, Maps, and Photos.
“Tap to Tweet” and “Tap to post” is integrated into noticiation center in iOS 6 allowing you to quickly update your social network status.
Facebook has also been integration into the App Store app allowing you to see what Applications your friends like, are playing, etc.