Nothing as change from dev preview 8,1 to official windows phone 8,1 same version OS nothing different but why dev preview users still need to downgrade to get cyan when user whit 8.0 can upgrade seems strange I think but after upgrade to cyan and 8.1 nothing change apart from the small arrows and some fix why they don't make user whit dev preview to upgrade I know the bit locker issue but no different from 8.1 dev and 8.1 official Cyan is firmware and 8.1 is OS cyan for me as no issue with dev because because firmware and OS are two thing different why fix for dev while is the same a ms the official release