One of my users is using fish in an otherwise zsh-only environment, so far we've only ran into problems once: virtualenv's activate script needs to be shell-specific to muck around with env variables. Every other tooling we use for webdev (npm, bower, whatever the kids are using now to pretend make doesn't exist, …) runs without problem.

Bass might provide some help with that.

https://github.com/edc/bass

I transitioned from zsh without any hassle, though I did need to port my environment variable config.

Fish works great in everyday use, especially the 'smart completion'. I didn't encounter shell scripts that wouldn't work in fish, since they don't run though fish, but sh or bash. Naturally some bash things don't work on the command line (for instance backticks), for these I usually quickly jump into a bash session, run the bash expressions, and then go back to fish.

Just take the plunge! Support for popular tools is better than it used to be. I've been using it for a few years now and it's been quite a while since I faced any sort of issues.

It's subjective of course, based on what your workflows are and how much bash-fu they involve.

I spent a long time feeling that way too, and then took the job one day. Turns out its generally fine - I had a bit of pain getting NVM to work, but otherwise its been really smooth.

What do you mean? The main limitation I know of is tab-completion.