I use Zsh, it's such a tremendous improvement over Bash. Not only does it handle parameter expansion much better than any Unix-style shell, but it also has a lot more useful built-ins that can save you from having to call out to external programs to do basic tasks, like getting the absolute path of the directory that contains the current script.

It is so unbelievably feature-rich that it's almost impossible to describe all of its features and merits, but you can safely ignore most of them and the basic day-to-day experience will just be "Bash, but better".

No program is perfect, but Zsh I think is pretty damn close. That's not because it doesn't have flaws (it definitely has flaws), it's because it does such a good job at doing what it does, that all its flaws seem minor and none of them fundamentally get in the way of it doing that job.

One additional thing I'll say is: it is probably the only Unix-style shell where I would feel comfortable writing 1000+-line applications with a CLI, tests, etc. I would never do such a thing with Bash or some minimal Posix-compatible shell. It's a very sensible system scripting language, alongside Python, Perl, etc.