As for YAML, yes, it's nice as a config file language or for storing info... but YAML parsers are harder to come by in less cool languages (non-Perl, non-Ruby, non-Python), and it's really meant to be human editable

This is one of my main issues with YAML. I don't see its niche as really being needed. You can either use Data::Dumper style serializers or XML for portability. YAML seems to muddy the waters to me. Although I am sure that there are a few edge cases where something like it is necessary; I think it gets overused just for "cool factor".