Lots of overlap in design goals with fish, except fish also places a premium on users interactively using the shell (which means friendlier in-repl experience but a balancing act when it comes to features). Fish’ auto completions are incredible, too.
Best of luck to them. Another interesting shell to check out is elvish, lots of new ideas there (even if awkward to use).
(Disclosure: I’m one of the core fish devs/maintainers. Edit: The entire team is awesome and the others deserve virtually all the credit!)
The goals of mine are akin to Fish in terms of REPL use but with a greater emphasis on scripting.
Like Fish, murex also does man page parsing (in fact I wrote mine before realising Fish did the same), but unlike fish autocompletions can be defined by a flat JSON file (much like Terraform) as well as dynamically with code.
Currently I'm working on murexes event system so you can have the shell trigger code upon events like file system changes.
My ultimate aim is to make murex a goto tool systems administration tool - if just for myself - but the project is still young