Sony Xperia ZR upgrade to Android 4.3 was rolled out recently. I decided to upgrade. First off, I am a Linux user, who was forcibly sold Windows 8 by Lenovo, when I bought their Z580 laptop. In hindsight, this was a good thing, as I find to my chagrin, that the Sony Xperia ZR Android 4.3 upgrade cannot be done over the air (OTA), but requires you to install the Sony PC Companion. Sony also does not have any support whatsoever for the Linux Operating System, even though Android is Linux Inside :0).
I downloaded the PC Companion. Next, took backups of your contacts, or any other important information on the phone and the internal storage (only important user files). The rest was left as is … to chance.
Install the PC Companion in Windows. When you connect the Sony Xperia phone to the computer, you will also find another download triggered. The computer triggers off the download of drivers for the Sony Xperia from the Microsoft website. Basically, Windows tells you here that you need to get the Xperia drivers from Microsoft. Ridiculous! Albeit to prevent you from getting malware infested drivers. This step is a waste of time. Refer this post on how to muzzle the DSMService. Make sure you stop the service now. This is one of the reasons why the download takes time.
The other reason the download could be slow is the traffic to the Sony servers to download the firmware. It took about 4 hours to download. The last upgrade 4.2.2 was installed over the air in about 30 minutes.