They help in pre-selling, direct traffic from the articles to your site and also backlinks. I know one disadvantage for doing it though. This is the fact that you are writing similar content about your site, which then gets placed on other sites. Now if them sites are rather seo'd, then it could be the fact that instead of you having rankings for a certain keyword, it could get replaced by a few article directories for your ranking which is not really what you would want.