u can read it here --> K850 Firmware Overview : Software, Firmware and Drivers : Sony Ericsson @ Esato
i will use my R1CA037 firmware because i don't have any problem with it...
i really want to use the latest R1EA031 firmware but it's too risky to BROD my phone.. so it's better waiting for the stable firmware... all i need to do is "waiting" :(