Have you read
http://www.gottabemobile.com/2013/11/21/att-galaxy-note-2-android-4-3-update-close/? I chatted with Samsung tech support and their response was consistent to what is mentioned in the article, that Samsung thinks AT&T released the update. Before I chatted with them though, I checked for updates on my phone and Kies, and my phone said the software is up to date (4.1.2, UCAMH3). Clearly, the update has not been released, given that no one here or on other forums have excitedly stated that they got the update.
When I mentioned to the tech support rep that there has been no tech news articles announcing the availability of the update and how no one in various forums have received the update, he then told me that the update was put on hold because of some software issue. I pried a little, asking what kind of issues are keeping it on hold, but all I got was "The software update for Samsung Galaxy Note is temporarily on hold while AT&T and Samsung look into potential improvements." That sounded familiar...
...and that's because I read from several sources online that the AT&T Galaxy S4's update was put on hold for the exact same reason. The update for the S3 was put on hold due to people reporting big problems after updating, and now it's live again.
I also asked the rep if he could tell me when the update will be made available again, only to get that canned response telling me that he can't speculate. I had actually half-expected to get this response, but you never know; some reps have disclosed information about future updates.
I encourage you to chat with Samsung so that other reps can also be made aware that despite Samsung's web site for the AT&T Note 2 saying that it's running 4.3, no update has been released. Maybe there really is a problem with our update, or maybe AT&T hasn't released it yet at all. Those who are analytical about things like this can look into why we haven't gotten the update when the Sprint version and all versions (except Verizon's) of the S3 (which, as we know, has similar characteristics to the Note 2) got it as well.