Sony Mobile is currently rolling out a new firmware update for the Xperia Z1 (C690X) with firmware build number 14.2.A.1.136. This latest update moves the firmware version from 14.2.A.0.XXX from the current build (14.2.A.0.290) to 14.2.A.1.XXX, so it’s a reasonable update.
This update adds a new setting for display calibration, allowing users to change the white balance of the display. The update should also fix a number of bugs that people are having with the Android 4.3 build. The FTF firmware file can be downloaded here. If you have downloaded the update yourself, let us know what changes you have noticed in the comments below.