One of the most beneficial aspects of posting unique articles to different article directories is the fact that, for each of these articles that you post online, you will receive at least one (probably more) links back to your site.
This is important because Google keeps track of html links to your site to judge how well your page will rank for various search phrases. This is why Google calls the different levels or grades you can get PageRank.
PageRank is graded on a scale of 1-10, 10 being perfect. I am pretty sure only Google.com has a rating of 10. The further up the scale you get, the harder it is to get an upgraded PR. Having a PageRank of 1 means Google acknowledges your sites existence and you are not trying to do something illegal.
Both the number of backlinks and the source of your links are important for obtaining a favorable PageRank from Google. Reputable article directories that reject junk (gibberish) articles will most likely have a better reputation, thus giving you a better PR boost for every unique article they post which contains links to your site. The more of these links you accumulate, the greater number of PR boosts your site will receive.
Of course, having all of this exposure on various reputable article directories will also create opportunities for people to click on the links and bring them back to your site directly. This is good, but not nearly as powerful as getting higher organic search rankings on Google -- there is no end to the amount of traffic that you might receive from good placement on basic Google search terms.
Here is how building backlinks and improving your Google PR relates to Spinbot.com: Spinbot will help you create an exponentially greater number of meaningful, readable articles that you can post to any number of article directories. The more of these articles you post to various directories, the more linkage and PR boost you will receive, not to mention direct click traffic.
Also worth noting is that these unique article postings will show up perfectly well on Google (no duplicate content penalty) since Spinbot will do such an effective job spinning them.
Ready? Right now you can start using Spinbot right now to increase your website's SEO rankings using the abovementioned methodology today, for free -- Go for it!