See http://isrssdead.com

For my part I'm currently building and updating a feedreader / feedparser kit that lets you build a newsfeed in minutes [1] or use a ready-made client such as rubynews [2]

[1]: https://github.com/feedreader/news.rb [2]: https://github.com/planetruby/planet/tree/master/rubynews

PS: The stats on Planet Ruby for RSS vs ATOM are:

Q: What feed formats are in use? Formats (n=51)

  atom        (52%) | ******************************* 27

  rss 2.0     (47%) | **************************** 24