My recommendation to application developers today is to use Atom 1.0, not RSS, as the basis for your content syndication.
DeWitt is the lead engineer at Amazon’s A9 search engine. He took a pretty detailed look at RSS 2.0 and Atom as part of A9’s syndication efforts (including OpenSearch) and shared some of his thoughts today on his blog. He appreciates the detailed implementation of the Atom Syndication Format allowing more lossless expression of data between content publisher and parser.