I’m currently using the Samsung Galaxy S4 LTE (from Zain) and I received an update notification regarding the new android 4.3 update for Samsung Galaxy S4.
So far I can’t really tell the difference, better color, yes, I haven’t installed Knox as its mainly for the corporate environment, and i didn’t want to fill my phone up, feels a little faster and more fluid. Will update you in the following days.
To check for updates for your phone, all you have to do is go to : Settings -> More -> About Device -> Software Update

Comments 2
I am the same as u but strangely i didn’t received it yet!!
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Have you tried manually checking for update? Also try searching for update while you are on wifi as some updates require wifi to be installed.