Samsung has been committed to bringing the latest Android operating system versions for their devices and this time Android 4.3 Jelly Bean to the Samsung Galaxy S3 which is the former flagship device and the roll-out should start in a few weeks time. If you are aware on how to flash a ROM manually you could go ahead and follow the procedures mentioned on SamMobile. Take care about the intricate details of your device and the compatibility.
The beta version is reportedly stable enough to work as a daily driver although it may have small bugs. It brings in a number of enhancements to the user interface which includes a new Settings Menu with tabbed interface as found on more recent Samsung devices. There is an addition of the transparent notification bar in the interface. Unfortunately the majority of the widgets in this build are still using the old design and Samsung Knox is not enabled. That should change in the final Android 4.3 Jelly Bean update for the Samsung Galaxy S3.Download : Android 4.3 Firmware