Article marketing is a tried and true method of website promotion. It's one of the best ways to get strong and permanent one way links back to your URL, which is of course great for SEO.
But there does seem to be some confusion about what the best approach is. Should you write one article and submit it repeatedly all over the place? Or should you write completely different articles that you submit to one or two article directories each?
On balance I think the second option is the best, for these reasons:
If you take the first option, Google will simply judge all but the original submission as duplicate content and try to screen them out of results. And while each backlink may be giving you a little bit of link juice there's no way that it'll be anywhere near as much as the original submission.
That said, If you have submitted scores or even hundreds of copies of the article, then perhaps this will accumulate to become quite powerful. And you can get mass submission tools to do this.
But this seems too much like clogging up the web! Why not help Google by writing one good article, and then relieve it of the hassle of having to filter out all the duplicates? Surely that's a good thing. Google is helping you by valuing those backlinks that you do leave in your author bio-boxes. So why not return the favor and help Google improve the quality of its results?
Of course many marketers get around this duplicate content filter by spinning their articles over and over again. But this just results in dozens of low quality versions. Many of them are pretty much gobbledygook. Simply out of a sense of pride I'm against this method, even if it works.
Really, it gets back down to quality. One good article at a well regarded article directory is pretty powerful SEO-wise. And once you've done it it's finished. You may end up getting further backlinks from it anyway because other people might publish it on their blogs and sites.
But after you've written and submitted it you can move on and start creating again. That's more enjoyable apart from anything else. By writing new stuff each time and submitting to different highly ranked article sites you'll keep it interesting for yourself and will probably end up with higher rankings in the long term.
Ultimately, it will also be better for your reputation, since people will obviously respect clearly written, thoughtful articles much more than software spun spam!