The international Galaxy Mega 6.3 started receiving the update to KitKat late last month, and now, US carrier AT&T has started pushing the update to its variant of Samsung's ex-largest phablet. The update includes the standard KitKat features we’ve seen on other Samsung devices that were updated to KitKat, including faster performance, white status bar icons, improved battery life, full-screen album art (which playing music) and a camera shortcut on the lock screen, wireless printing support, unified location control menu, and more. Furthermore, AT&T has preloaded a few apps, including Beats Music and ISIS Wallet, and has changed a few things around, including renaming AT&T Drive Mode to simply Drive Mode.
The update carries build number KOT49H.I527UCUBNE7 and is currently rolling out over the air. Remember, it will take time to reach every device, but you can try to pull it early by heading into the Settings » More » About device » Software update menu after connecting to a Wi-Fi network.