Galaxy S4
Sprint
Upgraded 4.2 to 4.3
MF9 to MJA
I had stock rooted 4.2 before; just installed the 4.3 update via Kies (which does not appear to be the recommended way to go if you're rooted; you're supposed to remove root first. So if you haven't updated, then don't do that -- find out what you're supposed to do -- but if you already have, then proceed).
Some people were having problems using CF Auto Root with 4.3 (definitely MJA, but I think it's a 4.3 thing) -- it would work but not install SuperSU -- but all I, and others, had to do was install SuperSU from the store and let it do its install when asked (I chose Normal install when prompted). People reported this in the forum, but the way they reported it was a bit confusing.