I just moved from an M1 Air to an M4 Air. I've had Mac laptops going all the way back to the G3 PowerBook era.
I loved the M1 Air design, and while the internals of the 2020 i5 Air were a bit lacking, it also felt solid. Before that I had a couple of 11" Airs in a row. All very solid, all had what I think of as that "Zippo lighter" quality where they felt very tough when closed, and over time picked up nicks and scratches (and even the occasional dent) with a sense that the machine was wearing in and getting some character.
So, now I have the M4. It's definitely a better machine in every measurable way than the M1, but I have to confess that 2 months in I'm still finding myself picking it up pretty gingerly. I don't feel the solidity I felt with the M1 and previous Airs. I feel like the tapered front edge of the M1 slipped better into my bag, and made it obvious at a glance which way it opened. I'm not hating on the M4 by any means. It's an incredible machine, but I have to say it just doesn't quite have the solid feeling I got from the previous Airs I had.
Also, even 2 months later, I still find the notch annoying as hell. Sorry. I get why it's there and the new camera is nice -- but I'm not sure the tradeoff is worth it to me