While I love most things about fish, I had to switch back to zsh because C-r in zsh (or even bash) is more efficient than fish's reverse-search functionality.

In zsh you can type-to-complete substring-matches in history. With fish, you can cycle to see what in your history matches your substring, but you can't easily modify your substring while searching to narrow down the match.

For example if I type "git re" and go up a few times, I may find that I'm only finding a bunch of "git reset"-ish commands, but I know I want a command like "git rebase", so in zsh or bash I would just type a "b" to narrow that down. But in fish I have to restart my search with C-c and try again with "git reb". Otherwise I'm just adding a "b" to the end of whatever the last match was, which isn't what I meant to do.

This may appear trivial, but I rely heavily on C-r for all my commands (which is one reason I like fish, because it predicted that correctly about me), but I rely on it for substring-matches, not just prefix-string matches like fish does with auto-suggestions.

I'm proposing that in addition to the existing reverse-search feature, a zsh-like C-r be implemented as well.