That's good; I think I would like to be able to use text/xml rather than just application/atom+xml for cases like http://www.environmentalhealthnews.org/archives_rss.jsp which can be subscribed to in bloglines _or_ viewed in my browser, because it starts with a stylesheet reference:
<?xml version="1.0" encoding="UTF-8" ?> <?xml-stylesheet type="text/xsl" href="/rss.xsl" media="screen" ?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
At the moment validator button blows up because it tries to validate the output of the stylesheet, but underneath is legal XML in UTF-8.