SharpReader, NetNewsWire rule them all
Index.xml is the most requested file of this website, it gets three times more request than index.php - time to have a look what News Aggregators people use.
Though the variety of available aggregators is huge, the top five aggregators have a market share of 75%: Most popular on Windows is SharpReader, most popular on Mac - unsurprisingly - NetNewsWire. Together, they have a 40% market share. Note how popular the newcomer FeedOnFeeds and the Outlook-plugin NewsGator are, and that the veterans AmphetaDesk and Radio UserLand play minor roles only.
So lets have a look at the CSS bar graph: