I purchased an S4 (i337 MF3) some time ago. I rooted it before researching and finding out that the bootloader could not be unlocked. When 4.3 became available from AT&T, it automatically downloaded and when I rebooted, the update failed. I unrooted, reset to factory a couple times and still unable to successfully update. Reading through forums, I realized that maybe my device is in some "limbo" root state since rebooting still displays "custom" with the unlocked padlock. My concern isn't necessarily getting 4.3 released from AT&T (I've heard of a lot of issues), but rather running into the same problems when 4.4 finally rolls out to the S4. Any input is greatly appreciated.