When I received my Kit Kat upgrade, the change was very minimal. The only thing that really changed was the lock screen. It was rather disappointing as Touch Wiz hid many of the extra benefits. For me, I am still on 4.4.2 and most devices are running on 4.4.4, including the S5. I know that the Kit Kat update took forever to the point when it came, it was almost forgotten. For me, that is one of the reasons why I will not get a Note 4 this time around and will probably go with a Moto X or Nexus 6