TL;DR the Fish shell is really very good, but is using an another shell something people care about?
For me it replaces Bash, with sh being the alternative when needed. Even for a casual CLI users it's better, and I've come to agree with the way they are making it, which has less syntax sugar and clunk than Bash.
Today I was trying an on demand http server that'll work with a media centre that is just VLC auto started and running full screen permanently, and using newsbeuter/podbeuterto fill a directory on a nas.
Rather than create a file, typing `funced news' and I'm in an editor on the cli with auto indentation and syntax colouring:
Brackets and quoting errors are visible, just like you'd expect from an editor, once tested it can be saved with 'funcsave news' and I think most lines show some differences to Bash.
I've also written a simple Telegram bot for an MTA and I'm basing a home automation system on Universal Variables with Events tied to them changing (via SSH or CGI), which is something I was looking to Python and SQLite for, I was impressed with Fish enough to try them.
I still use bash but if I was going to pick a different shell it wouldn't be for the language. A lot of the scripts I tend to write need to be portable. I did play around with zsh a bit which has a better API for writing customisation such as tab completion though. Still have yet to move over to it.
Why does everything think just because you are not running BASH you cannot script against it? Want to use FISH but still have portable scripts, awesome, do nothing, keep using the !#/bin/env bash she bang