A number of Android Central Forums members have reported receiving the update, which had a download size of 689.53MB. However, some forum members apparently have had issues with Google Play Services freezing up after installing the update (which has not been uncommon for Lollipop updates), so you might want to hold off downloading and installing for a little while to make sure all the ducks between AT&T, Google, and LG are in their appropriate rows.
Late last month, LG said that Lollipop updates would be coming for the LG G3 in the US "soon". A leaked software update schedule from Sprint indicated they plan to update their own LG G3 to Lollipop on Feb. 16, and with HTC and Samsung rolling out their own Lollipop updates across carriers, it's good to see AT&T and LG keeping the ball rolling.
Here's the word from AT&T:
Today AT&T launched the Android 5.0 "Lollipop" operating system for AT&T customers with an LG G3. The Lollipop update offers you a new bold and colorful interface, with new notification options, longer battery life, increased security against malware and automatic device encryption, settings for multiple device users, a new quick settings drop-down menu, better internet and blue-tooth connectivity, and voice activation even when your screen is off.