If you not receive any notifications for this update, you can check manually if the Update for Android 4.3 Jelly Bean is available or using Samsung Kies application.
This update makes the phone feel slightly faster. Also, we have Gear support with this update for both smartphone, and also for Galaxy Note 3.
I wish to announce the availability or update to 4.4 but it seems that it still will not be available very soon. Any official news about this update.
Have you upgraded your Galaxy S3 or S4 to Android 4.3? Did you experience any issues with it?