So for those that don't want to wait for the OTA update... go over to XDA and there is a thread where someone grabbed the zip file from their phone that got the OTA. Download that file, then rename to update.zip (it is originally named 321a2cb29b9c.update_SPH-L720_MDC_CSB_user_RP_to_MDL_CSB_user_RP.zip) and put it in the root directory of your SD card (you have to have an SD card installed)
Then boot into recovery. When the phone is powered off, hold down vol+, home, and power and keep holding them down. The phone boots up and you'll see the galaxy s4 logo and in small text at the top it says booting into recovery. Then let go of the power button but keep holding down vol+ and home until you get to a recovery menu. Use the vol keys to scroll through the options and the power button to chose an option. You should see an option for update via SD card and then chose the update.zip file.
It'll go through the process of updating and then reboot. That's it, you should then have the software update on your phone. At least it worked for me.
http://img.tapatalk.com/d/13/05/09/te8unu8y.jpg