Sorry I haven't posted much lately, I'm working on an RSS Schematron validator. I have it working for RSS 0.91/1.0/2.0 right now. It's pretty awesome. I jigged all the FeedValidator.orgtest cases into NUnit and started testing it. I'm going to add OPML and Atom. Not sure if I'll target Atom 0.3 or the release of Atom scheduled next spring.