US Cellular's variants of the Galaxy S III and Note II are slated to receive OTA updates to the MB1 build, which includes a bump to Android version 4.1.2 for the GS IIII (the previous Note II update here, previous GS III update here).
The Galaxy S III's release notes indicate only two changes: the aforementioned increase in OS version, and a fix for audio when playing streaming media (this may fix a long-reported issue with Netflix playback on the device).
Galaxy S III
Build JR003L.R530UVXMB1 - Android 4.1.2
Items updated, added, removed from the device:
- Android version Jelly Bean upgrade to v4.1.2
- Fixed audio issue with streaming media
The changes built into the Note II's update (build R950VXAMB1) are unknown, as it was already running Android 4.1.2.
The Galaxy S III update should be pushing over the air soon, but there are instructions on downloading and flashing it manually using the Simple Upgrade Tool here. The Note II has no such instructions, so you may have to wait for it to push to your device directly.