YAML is a pain to parse. And as a human, having to remember quoting string values like "yes" and "on" to prevent them from being interpreted as booleans in YAML really grinds my gears. I don't care if it's prettier; YAML can't disappear quick enough.

I wrote a haiku some years back to demonstrate how broken the Ruby implementation was.

    YAML:
      takes a no for a 'no': no
      spring,summer,fall,winter: 3,6,9,12
      the game is: on

Running it through ruby 2.3.1 yields..

    {"YAML"=>
      {"takes a no for a 'no'"=>false,
       "spring,summer,fall,winter"=>36912,
       "the game is"=>true}}