The 69MB update is available over Wifi only, brings new kernel and new radio
Build UCAMC3 looks like it's rolling out heavy for the AT&T branded Galaxy Note 2. Since last night, plenty of users are reporting that they have received the 69MB OTA. There's no official change log posted, but a quick chat with someone who has received it shows that you'll be getting a new radio and a new kernel. Besides the obvious performance boosts to the network that comes with new radio software, users are reporting better and stronger Wifi, and increased performance overall.
You'll need to be on Wifi to download this update, so be sure you're not using your cell radio when you check (right after reading this) lest you get the check again in 24 hours message. When and if AT&T posts any official list of changes, we'll update this post.