I am no SEO expert but I do use it to get thousands of visits to my websites everyday. In fact my whole life revolves around creating content and doing SEO. I use Article marketing along with guest blogging. Are they effective? Yes. I send out just as many articles as I put in my website so it is great for me. If I want to dominate Google I can, it all depends on time or getting someone to do it for me. The other thing is that I spend a lot of time maintaining the position of my best sales pages. If a sales page drops in sales I do a bit more article marketing or guest blogging to get back up the ranks. The links in the articles take a few weeks to show any results and people often give up as the results are not so obvious. Of course you get more benefits from a well respected website, rather than a new site with no reputation, but these links can count too.. You either need quality or quantity but preferably a bit of both.