I switched from i3 to Niri a couple weeks ago, and I've been super happy with it.

Niri feels like it lines up more naturally with the way I tend to use windows and workspaces. I'm working on one project per workspace, opening an occasional ephermeral terminal window or web browser to the right when I need to reference something or run a quick command. My other windows in the workspace aren't altered by these new ones, no reflow happens, and then I can close it when done.

My only problem with Niri is that now I really want an Ultrawide monitor.