Dave Shea at Mezzoblue wrote today about Plugging the RSS Usability Hole, where he finally gave a good reason for styling RSS feeds: so that unsuspecting users who click an RSS link see something intelligible. It's good idea, so I did it on this site. I also wrote a page to help explain RSS while I was at it.
If you haven't heard of this idea yet: the RSS feed includes an XSLT stylesheet reference, so if it is loaded into a browser, the XSLT will transform the XML gibberish into pleasantly laid out readable HTML. RSS readers ignore the stylesheet reference, so they continue to read the XML directly as before.