As much as possible, syntax looks like shell commands, and blocks uniformly end with `end`. You don't get the messy inconsistency of sh where functions use braces and conditionals use ALGOL-style `fi` and `esac` and loops use `done`. Beyond that, some control structures even support flags: if you want to read up on function definition you can run `function --help`, and if you want to define a function `foo` that completes like `git` you define it with `function foo --wraps=git; ...; end`. That means you have to keep less in your head.

A lot of things are even defined as ordinary fish functions. In sh, aliases are a dark and evil feature that hooks into the parser and can be used to create rudimentary macros. They have some really surprising behavior. But in fish, `alias` is a shell function and you can get the complete source code on your screen by running `type alias`. It doesn't do any evil things because it can only do things you could do yourself.

Fish has sensible variables and arrays. All variables can be arrays. When unquoted, variables expand like "$@" in sh, so packing multiple arguments inside a variable is trivial and there's no need to worry about whitespace. Command output splits on newlines, which means that things like `for file in (find . -iname 'foo')` just work, assuming you don't have newlines in your filenames.

Writing one-liners in fish makes me much less anxious then doing so in sh.