Pick up that Galaxy S4 that is totally not going to explode and give it a glance. Sprint customers might just see the MF9 update begging for attention. Don't expect anything too major here, but after the download is complete, your phones should support installing apps from the Play Store onto MicroSD cards. Other niceties include HD Voice enhancements and additional wallpapers.
This is an OTA update, so there's no need to whip out the USB cable and fire up Kies.