I always wondered why anyone would do this. IMHO modality and shells just don't get along well. Besides that, readline-like bindings are both good enough and you're likely to encounter them in the wild when working with ssh, database prompts, and so on.

Yep, what kind of issues you had? Works well for me. Not sure what do you mean by efficiently -- but my tip is pressing alt-e to edit the command in external editor when it's multiline (although it's not limited to vi mode in fish)

It interacts pretty poorly with, e.g., terminals in IDEs, but is essential for my day to day in my regular terminal emulator. Worth noting I'm not a vim power user, but I could live without vim keybindings for moving around, it just feels more naturally.

I have tried vim mode in fish and I didn't like it. I find I don't really need vim bindings in the shell because I'm almost never editing. Alt+e to open the current command line in my editor works really well for me when I do want vim.