Sony has started pushing out an update to the Xperia Z, ZL and ZR yesterday that builds on the previous jump to Android 4.2.2 with several fixes and improvements. We have just pulled down the v10.3.1.A.0.244 update on our own Xperia ZL (C6506 model) via the Sony Bridge for Mac application, but the update is supposedly pushing out OTA (over-the-air) as well.
While we don't notice any immediate changes, across all three devices users are reporting various subtle fixes such as a smoother boot animation, more efficient RAM management, improved 3G signal strength and touch response. A couple of camera changes have been made as well, giving access to high resolution images when not using HDR and improving low light performance.
Other fixes reported are sleep and wake times improving, fixing screen flicker and fixing unusual battery readings. While we never saw these issues on our own Xperia ZL, it's good to see Sony following up with minor updates to fix a group of small issues. Together with the big update these devices received to Android 4.2.2 recently, Sony is clearly taking updates to its devices seriously.