Initial reports of users receiving the update has begun, still no official change log.
After its first major update from Ice Cream Sandwich to Jelly Bean earlier this year, the AT&T Samsung Galaxy S3 is receiving another considerable update. The phone will still be on Android Jelly Bean, but it gets a version bump from Android 4.1.1 up to Android 4.1.2 (build JZO54K.I747UCDMG2).
Users are reporting an update file size of over 220 MB, which is definitely on the larger side. Some have had success downloading over LTE, while others have said they were forced to download over WiFi. It is also being reported by users that this update includes Samsung's multiwindow feature.
Keep an eye out for that update notification, and join the rest of our members in the forums to discuss the changes and fixes in the AT&T Galaxy S3's latest update.
Thanks, xisruno and Keith!