iOS 6 Offers New Wi-Fi Plus Cellular Mode
iOS 6 Beta 4 brings a new feature called Wi-Fi Plus Cellular that lets apps having trouble with poor Wi-Fi use cellular data instead.
The feature is accessible from the Settings -> General -> Cellular menu.
Also new in iOS 6 is the ability to decide whether to use cellular data for iCloud Documents, iTunes, FaceTime, Passbook Updates, and Reading List.
Take a look at the screenshot below.