I did read the docs for coredata last night and immediately flame the developers for exactly the short sightedness I expected from them a couple months ago.
Specifically, there is no way to write your own data store adaptor as the api remains private. So you can't use CD with legacy file formats. As the team was so busy being secretive and working in a vacuum, I was quite certain they'd bone the poodle in some way and they have lived down to my expectations. Seems they never bothered to think CD would be useful for editing a specifically formatted file like an RSS document.
RSS would be a great CD app as it has a well defined structure from which you can extract an object model, but it requires a particular file format as well.
To quote Asimov - Stupid Asses.