Some things I've noticed that I don't think have been mentioned here.
Smart Lock with trusted device: My phone remains unlocked while in range with my Pebble watch. Works great with Unlock With Home Button and No Need for OK on PIN. I have iris detection should there be a bluetooth glitch.
Disable Floating Icon for Air Command: It kept popping up in drawing apps when I got near it. Now I just click the pen side button.
If you have a favourite widget that now looks too small on the new, amazing screen you can adjust this in Settings->Display->Screen zoom and font
Shunt the zoom to the middle and then drop the font size town 2 notches to compensate.
In the gallery, inside an album, you can pinch and zoom to adjust thumbnail size.
Black backgrounds save a shed load of battery. They also look nice with the case of the black edition of the phone.
You can also download dark themes from Walpapers and themes so that things like settings and phone etc are dark. I use Material Black.
Substratum is great for setting dark themes across non Samsung apps.