It's not one killer feature, but it's a lot of small things that add up to this feeling that POSIX shells are stuck in a rut and that a better world is possible.

I'm going to use docker output as an example. I know that you can ask docker for json and then use jq, but let's pretend that what you're working with isn't so friendly as docker. Here's the output of "docker ps", a string:

    CONTAINER ID   IMAGE            COMMAND                  CREATED       STATUS       PORTS                   
    786fc8348b7a   postgres:12.6    "docker-entrypoint.s…"   9 hours ago   Up 9 hours   127.0.0.1:5432->5432/tcp

    line=$(docker ps | grep postgres)
    echo $line | awk '{print $2}'
    echo $line | awk -F 'ago' '{print $2}' | sed 's/hours.*/hours/'

    postgres:12.6
    Up 9 hours

     $ docker ps | detect columns --guess | where ($it.IMAGE =~ postgres) | select IMAGE STATUS

    ╭───┬───────────────┬────────────╮
    │ # │     IMAGE     │   STATUS   │
    ├───┼───────────────┼────────────┤
    │ 0 │ postgres:12.6 │ Up 9 hours │
    ╰───┴───────────────┴────────────╯

Powershell feels to me like it's made by people who want all data to be structured, and who expect the app to do the work of structuring it for them. nushell feels like it's made by people who understand that text is king, and who are willing to attempt taming that beast as-is.

Plus there are a lot of batteries-included things that just feel nicer. Like if you want to make an http post request, the command is "http post". Of course you can still use curl, but I feel like this is so much more readable:

      $ let token = "REDACTED"
      ( http post
          -H {Circle-Token : $token}
          --content-type application/json
          "https://circleci.com/api/v2/project/gh/job/myproject/pipeline"
          {  branch: "main",  parameters:  { action: "dothething" }}
      )

    $ 5 + "5"

    Error: nu::parser::unsupported_operation
    × addition is not supported between int and string.
       ╭─[entry #208:1:1]
     1 │ 5 + "5"
       · ┬ ┬ ─┬─
       · │ │  ╰── string
       · │ ╰── doesn't support these values
       · ╰── int
       ╰────