About once a month :-)

I suspect that the XML format might be easier to work with than the flat files, but I must confess ignorance. You're quite correct that most of the work on the ontologies by the GO consortium itself uses the flat files with editors/browsers such as DAG-Edit and AmiGO. At present the flat files in the GO CVS are the most up-to-date version of the ontology (I think).

Tim

Disclaimer: I'm just an interested party with little to no inside experience; I don't speak for GO :-)