The main issue I had with TOML is how much more syntactically noisy it is. Equivalent files with 2-3 levels of nesting usually become at least 50% longer than equivalent YAML.
More here : https://hitchdev.com/strictyaml/why-not/toml/
More here : https://hitchdev.com/strictyaml/why-not/toml/
I have some projects where I'm frequently writing and midifying content that resembles the example here, and I use YAML there and plan to keep using YAML. For most other things, I'm just doing configuration, so I use TOML. No reason you need to stick to one or the other.