YAML IS AWESOME. As a configuration language, It is fast, flexible, metaprogrammable.
It would NOT be a big change, In-Fact it would be a dropin replacement because JSON is a valid subset of YAML.
All current JSON config files would work perfectly when being parsed by the YAML, making this the perfect time to switch over.
People won't even have to know that PyYaml is actually parsing their Json file.
In additon to this, YAML has some really cool features such as anchors which allow us to reduce repetition in config files (define once, use many times.)
From the wiki definition:
So please, reconsider YAML. It's awesome, It's powerful, It's a drop-in replacement.