What about fish? I use it on the terminal but still write my shell scripts in bash so they work across systems (including windows with minGW). I think a big issue with new shell adoption is the prevalence of bash basically everywhere.
Fish does have bugs though. I've seen enough stack traces while running early builds to question the security (although I'm sure we all remember the bash shell-shcok bug that was laying around for years).
If you haven't tried fish, I highly recommend it. It takes a little getting use to, but overall it adds a lot of really amazing functionality that I find really useful.
Serious question (that I've asked elsethread): what does fish offer than zsh & bash lack? A quick perusal of the docs reveals nothing obvious, but … I could be missing stuff.
* Instant auto suggestions, you just type stuff, like in a web browser.
* Sane defaults, no need to bring around your own config. On a new machine I just install fish, run fish_config and customize the prompt with the web UI.
* Scripting with simple syntax, especially for one-liners. Yes, fish is incompatible with bash, but it's less of issue in this case.
Which is better than the days when csh and different Bourne flavors were common.