120 Hz can also noticeably improve frame pacing for 24p video*.
120 Hz vs 144 Hz? Barely noticeable when flipping between the two. Not sure if I'd pass an ABX test with 100% accuracy.
Can't speak for 240 Hz or higher, as I haven't used them.
* Though 119.88 Hz is probably a better default for this since most non-DCI "24p" video is still 23.976 FPS; this is changing, but until browsers and streaming apps support VRR for video, I'm not convinced this is a good thing due to the mountain of legacy 23.976 FPS content.
It's night and day when you're going back and forth between looking at them and wiggle your mouse around in circle. But after a few seconds of being focused on your work, you're not thinking about it anymore.
Being able to watch 24fps video without non-integer frame weirdness is the only real advantage outside of twitch-reaction gaming.