According to Xperiablog, this primarily focuses on bug fixes but might have some feature enhancements hidden inside it. Since there are no official changelogs that are currently available, it is difficult to predict exactly what changes this update brings.
One of the member of XDA forum confirms that he has received the update on his device, thus it mustn’t take too long for this update to arrive on your device.
Since this update is presented as an OTA (Over-The-Air) update, it will be released in gradual steps, thus you might not have received this update automatically. Once the update is available for your device, you will receive an official update message on your device’s notification screen. Just tap on this update and follow the onscreen instructions to install the update.
Periodically check for the update yourself to see if an update is ready for your device. To check for the update manually go to Settings> About phone > Software updates > System updates. If an update is available, you will be notified, just follow the onscreen instructions.
Although some users have reported that they have received and installed Three Austria Xperia Z (C6603) Firmware update build 10.5.A.0.233, there is no news as to when Sony will roll out this update for other carriers.
This firmware update build 10.5.A.0.233 is also scheduled to be released for Xperia Z (C6602), Xperia ZL (C6502, C6503, C6506), Xperia Tablet Z( SGP321, SGP341, SGP351) and Xperia ZR (C5502, C5503) variants since they have all received PTCRB Certifications.
If any Three Austria Xperia Z user received this update then please mention in comments what fixes did this update brings. Do you find your device smoother than before? Are there any hidden or new features?