While I don't mind YAML for relatively simple data files, I find it to be very difficult to use when there are more than one or two levels of nesting. If you have a relatively complex config file, then I find JSON to be a much easier to reason about and make any necessary changes.
For current versions of YAML, JSON files are a subset of the YAML standard. Thus any compliant YAML parser will also parson JSON.
The place where I use this trick the most often is in .kitchen.yml files used by TestKitchen when writing Chef cookbooks. I start out by taking an existing .kitchen.yml file and converting it to
.kitchen.json using this website http://codebeautify.org/yaml-to-json-xml-csv. I then copy the
.kitchen.json to .kitchen.yml.