TOML config files are used heavily in my product for developer-facing features. I personally think it's the cleaner compared to YAML + JSON.

It also benefits from being easier to copy + paste configs from docs since the entire path is included in each block; users don't have to worry about setting up the correct hierarchy.

Regardless, I strongly agree with points #1-#3. I also wish there was a way to support something similar to inline YAML schemas to catch users' typos in their IDE.

I would love to use HCL or potentially Ion, but IDE support and widespread acceptance isn't strong enough yet.