RSS vs Atom
My simple thought on the RSS vs Atom debate: RSS not having any way to identify a particular item, a unique key, makes it difficult to implement well. You have to come up with heuristics to figure out, given an RSS feed and the set of tags the publisher has chosen to include, how to uniquely identify an item. Sometimes it comes down to checksumming the content, which means if the user edits the post, there's absolutely no way to distinguish it from the original.
If RSS 2.0 required a guid, then I'd be on the side that says that Atom is unnecessary.
Of course, we're really no further ahead since some publishers will use RSS and some Atom, so software will have to support both anyway. But at least if a user subscribes to an Atom feed, they won't see as many duplicates. Maybe the users will figure this out on their own and eventually come to prefer Atom.
(Yes RSS specifies a guid field, but it's optional. With an Atom feed you know it's there).