I've used Emacs for over 20 years and I have been meaning to switch to vi keybindings for a while (but haven't yet :). I just find myself executing long commands with only 4 of my fingers engaged, because one of them is holding a modifier key, and it's somewhat uncomfortable. Not injury-causing uncomfortable, but enough to make me think "hey, I think the other team got this right." I would not mind switching between command and insert modes; I can keep the state in my head instead of in my finger.

The barrier to switching, for me, is that the vi-like modes are set up by default to have vi-like keybindings, and I just don't care to go in and change them all to Emacs-alike keys, and I worry how flexible other software with "vi mode" will be about that. I am past the point where I'm going to use hjkl to move the cursor around, I use npfb. I can easily change the details in Emacs/Viper, but then how am I going to use anything else, like the shell? That is my main worry.