For what it's worth, I probably wouldn't have noticed if I were going from an older Air to the new Air, but it is very noticeable going from a 3rd generation pro with Pro-motion after 4+ years, and seeing them side by side, I immediately noticed it. At first I thought it was because of all the apps updating in the background.
I'll eventually (hopefully) get used to it as I can't justify the extra $350 for a smooth scroll. Hell, for an extra $80 I can get a Series 9 watch also. I tested a couple of games and videos and I didn't really notice it much there. Its mainly on scrolling web pages, or the main screens. It's a nice iPad and an upgrade in processor over what I had. I was mainly wanting to get into the M series family, and i got better wifi, better front camera. The other features of the new Pro aren't a necessity for me personally. I don't use it for photos, for speakers/mic I am usually plugged in with my AirPods, and the thunderbolt... well, not sure I'll use that. Overall it's a great pad, the Air 13in. Maybe in a year I'll upgrade to the pro and have that WOW feeling again.