Based on the latest Official Sony ICS 4.1.B.0.587
- Copy the zip file to your SD card
- Reboot your device in CWM
- Make a full data wipe-factory reset
- Wipe cache and Dalvik cache
- Choose install zip from sd card
- Wait for installation to finish, reboot and follow the sony setup wizard through the rest of the setup process
- Reboot again and enjoy!
Please report me the bugs!