It will take some getting used to when setup correctly but the result is a greater picture quality.
I kept the setting on "Automatic" and calibrate my TV settings instead to get the best result.
Because when I set it to FULL, I get crushed black and over saturated color. To some people this actually looks better but it's not how the image is suppose to be. I don't like crushed black and over saturated color like that BF4 xbox one footage from Digital Foundry. To me, that looks like s**t and unnatural.
I work with graphics for a living, for better results, leave the PS4 settings at default and properly calibrate your TV instead.