Ian Ward, Development Seed, not only makes some good points about the inclusion of CSS within an RSS feed, but he also that the "look" of the feed varies from RSS reader to RSS reader. Hopefully, in the future the Internet gods will be kind. I personally don't want to worry about how my CMS looks in a browser and an RSS reader.

Development Seed: Optimizing the look of your syndicated content - Just like the large number of different web browsers that you need to design for (you have Internet Explorer, Netscape, Mozilla Firefox, Mozilla, Safari, Mac Firefox, Mac Internet Explorer, etc.), there are also a ton of RSS readers. On top of that, RSS readers can be desktop based or web based – similarly to email with desktop email like Outlook or Lotus Notes and web-based email like Gmail or Hotmail. From a web designer's or content publisher's perspective, a person in these trades needs to be aware that the content they are publishing on their site will look good no matter where a user sees it. [Planet Drupal]