If you're working a lot in the terminal, than fish's convenient auto-suggestion mechanism is really quite a game changer, and it really "feels" 3x more productive because the prediction is pretty good (each directory has its own command history which fish checks first for matches). It's like replacing a traditional search box which only shows exact matches after you hit Enter with a fuzzy-search-box which immediately displays a most likely match while you're typing.

There are plugins for zsh (and maybe other shells) which emulate this feature though.