The MSI Oculux NXG251R is the first monitor I've owned with a high refresh rate and g sync. I know a lot of gamers ask themselves if these features are really worth it -- because I asked myself those same things -- and I can now confidently say that, yes, you will notice and it will change the way you play games and you won't ever want to go back. These features aren't luxuries, they impact your play at a fundamental level.
Aesthetically, the high refresh rate makes the game so much more fluid and immersive. Performance-wise, having an adaptive refresh rate on fights where you're whipping your camera around or moving a lot lets you focus on the action and not the pixels.