US Cellular has listed the official changelog for the Galaxy S4 Android 4.3 Jelly Bean update. Starting with the already known enhancements and features brought by Samsung's official firmware (which includes Samsung KNOX and Galaxy Gear smart watch support). The carrier has updated many of their own pre-installed apps, which include City ID, Mobile TV, MobiTiles, WiFi Now, Mobile Security etc.
Looks like almost all carriers have updated their respective Galaxy S4 variants to Android 4.3 Jelly Bean. Well, that was far quicker than we had expected. Usually, carrier updates come in months after the international, unlocked variant gets updated. That doesn't seem to be the case with the Samsung Galaxy S4, and that's a good thing.