Users of the AT&T Galaxy S4 have been reporting that their devices are receiving updates, and are reporting smoother perfomance because of it.
The Galaxy S4 has launched to mostly universal praise by the media and users alike. There weren't many gripes with the device's performance but many users and various outlets did notice that the operating system seems to stutter or become sluggish during certain activities. Considering the high specifications of the device, it wasn't hard to deduce that the cause for these issues must have been software related. Well, it seems Samsung may have solved some of those problems.
Users of the AT&T version of the Galaxy S4 on the Android Central forums are reporting that they are receiving the updates on their phones, and after installing them they are noticing smoother performance across the board. There are even some reporting possible improvements with the camera. Although it should be mentioned that none of this is confirmed, because, as of now, there is no official changelog from Samsung.
Nothing here is too unbelievable though, so hopefully it doesn't take too long for devices on other carriers around the world to receive the update.
Source: Android Central