Seriously, if you haven't upgraded your desktop PC to a higher refresh rate screen yet: It's the biggest "feels like a new computer!" upgrade since we swapped HDDs for SSDs and the days when your new CPU was 2.5x as fast as the old one. There is no turning back after having experienced the buttery smoothness, and the impact is IMHO higher during regular usage than during games.
Last week I went to 240 hz and while it's noticeably even smoother, it wasn't nearly the upgrade, so there's certainly diminishing returns. Though I did go from IPS to OLED and THAT is really nice.
This is usually the point where someone will chime in and say something dumb like "The human eye can't see more than X frames per second" which is just hogwash. It's not about individual frames, but the fluidity of motion. At 60 fps, an object moving across the screen is moving 4x as many pixels per frame as 240 fps. When you get used to 240 fps, 60 fps feels like it's strobing.
Still quite frustrating that the display industry did it again in specifying a standard that makes most of what's interesting about it optional, so everyone can print it on their boxes without delivering the expected value.
It's an impactful and noticeable upgrade in addition to everything else being awesome, but for me it doesn't come close to being the the most important. If all else was equal or better, and I had to pick between 6k resolution or high refresh rate, I'd have a hard time picking refresh rate, but I'd prefer both.