Android 4.2.2 Jelly Bean update for the Xperia Z has finally started rolling out. The version number for the update is 10.3.A.0.423 . Currently the update is live in Spain and the Ukraine for the LTE model (C6603) and for the carrier variants in Austria, Czech Republic, Hungary and the Netherlands. It also also available in Taiwan for the HSPA+ version (C6602).
The Android 4.2.2 update for the Xperia Z would bring Latest version of Sony Media Apps with seamless integrated services, my Xperia security application, New Customizable navigation bar with quick settings with up to 10 toggles, New widget functionalities for lockscreen and homescreen and lots more new features. It would be rolled out gradually, hence it might vary across different carriers and countries.