Yes. I have a M1 8GB MacBook Air that I use as a lightweight travel machine, and macOS 26 utterly trashed the performance on it. Things I used to do fine (work on small Xcode projects) were completely unusable, to the point where I had to downgrade it to Sequoia.

I've been running it on the macOS 27 beta all summer, and it's night and day. It's usable again.