While the Sony Xperia Z Ultra just became a Google Play Edition device, owners of the Xperia Z and Xperia ZL also have a reason to be happy. The Android 4.3 update for Sony Xperia Z, as well as the ZL, is now available to download, thanks to XDA Developers.
The Xperia Z’s firmware (C6603) and the C6503 for the ZL are both available at the source links below. Build numbers are 10.4.B.0.569, but it is not yet known whether this specific version of the firmware will the the final one which will be pushed out to devices by Sony. The source of these leaked ROMs tagged them with “Commercial&Journalists” description, so you might want to read through the threads for feedback, bug reports, and alike.