I've been running the beta OS for months. Never tried Stage Manager. I just turned it on and so far... I'm actually really liking it! It's basically like having one desktop per app. Maybe as I use it more the complaints will make more sense to me.
I turned stage manager on after learning about it from the article. Maybe it's my OS version, but it's super buggy, and I can't seem to turn it off. I'm with the author on this one :\
Update: closing and reopening the windows puts them back into normal mode. Apparently the little close buttons in the sidebar still work (along with the rest of the window). Really weird...
I'm looking forward to trying it. There's been a million ways to manage desktops and windows, and there probably never will be the perfect one. I'm all in favor of experimentation in this area.