Matt Cutts vaguely referenced description tags back in the dark ages: http://googlewebmastercentral.blogspot.com/2009/09/google-does-not-use-keywords-meta-tag.html, and left the impression that their content was of little SEO value. The time has come to define the purpose of SEO and our true objective as specialists in the field. SEO is a misnomer that frequently leads talented, motivated people in the wrong direction. While much of our efforts seem to be directed at appeasing the search engines, in reality we should be focused upon the target market. While the search engines (and W3c) specify the structure, content is a market issue.
At every opportunity presented to us, we need to offer content that will generate an action. Description tags clearly present that opportunity regardless whether the individual words are indexed for search purposes. My experience confirms my conviction that description tags are an intrinsic element in enhanced website performance.