The first two solutions are iOS6+ only, and the UDID never worked on iOS6. People who can live with cutting off iOS5 don't have a problem by definition.
Ubiquity container: Does anyone use and track this? How many % of people have iCloud enabled for third-party apps? (Just asking because I turn this off on all devices; I don't have any app that uses this, so all I am disabling is abuse)