I've used Play! for work and personal projects, and I've never had to deal with XML. Play uses .properties files for simple things (actually, there's just one main .properties file), YML for more complex data (like a list of fixtures to load for unit testing), and "convention" for pretty much everything else (that is, you don't have to write any configuration if you put things in the places where Play expects them)

Play doesn't use xml for configuration. It has a simple property file. So, none.