AT&T rolled out the Android 4.3 update for the Galaxy S4 in the United States, but it didn't last long. After a couple of days users started reporting issues with their Samsung devices and AT&T put on hold the update.

Now, about a week later a new, 719MB, build of the update has again been released, hopefully free of bugs. It is supposed to update users S4, adding new features like Galaxy Gear, Samsung Knox, Group Play 2.5, drag and drop to uninstall or disable applications, as well as some stability improvements.

Source