When I read "gbq enabled: yes" I don't worry about whether it's a string or a boolean when reading it, I worry about whether it's a string or a boolean when I want to change it and it gets parsed again.
I think a lack of type safety is the main problem with YAML - a wrong indentation, a typo in a key, a string that gets parsed as a boolean, etc.
Other than that I think it's a great format - terse and far less syntactic noise than other formats. This is why I wrote https://github.com/crdoconnor/strictyaml so people could write type safe yaml and get instantaneous, clear error messages on those things.
No coercion of y/n/yes/no/on/off to booleans (these were also removed in the official YAML 1.2 spec, thankfully), no direct object representations, no anchors or references, etc.