I get the feeling that it does make a difference. Ever since I created a WordPress blog and added quality articles each day, Google started visiting my site every day instead of once per week or two. Plus my grey PageRank bars went from grey to white on even my older pages (inbetween the major updates). That PageRank change never happened to me like that and I know only the really good sites seem to get that kind of treatment. So yes, it does. I would add a blog and updated it every day since it's easier to sit down and write something "informal" instead of spending hours and hours writing the perfect permanent static pages.