This is a great question, since The Winery Web Site Report includes "RSS feed and/or Web log" as one of its 25 rating elements (although, to be fair, it doesn't carry the same weight as your site navigation does).
In short order, I should be able to answer Tom's question definitively -- our database of over 2,400 site evaluations is nearly complete. But it's almost certainly a number less than 24 (1% of all sites). Last January, Tom asked whether he'd found the perfect winery Web site, just after I'd started work on The Winery Web Site Report. At some point in the not-too-far-future, I'll answer that question too.