Xda-developer legend DooMLoRD has just released a pre-rooted Jelly Bean ROM (6.2.B.0.200) for the Xperia S. The ROM can be installed using ClockwordMod Recovery and will work for those with locked and unlocked bootloaders. Users of Xperia S and Xperia SL can download the ROM. You can find more information here.
Thanks DooMLoRD!