I recently logged in to my account at ArticlesBase after a long hiatus. I got a really nice surprise. My articles had racked up many thousands of views over that time.
I don't have that many articles up on the site. And I didn't do any real keyword research before submitting them. So, this particular directory is clearly very good for SEO, and also gets a lot of traffic.
Also they've got a great statistics section. So you can get a really good idea of how people are finding your articles. (Actually, that's what surprised me. I was ranking for quite a few keyword phrases without really trying.)
The only downside is that the author bio-box links are nofollow. But then I suspect that's part of the reason ArticlesBase is doing so well. It's keeping a lot of its "search engine juice" contained withing the site.
So, when you submit articles there you won't get any direct search engine benefit. But it will certainly be worth doing so for raising your profile, and those direct clicks are sure to add up to something substantial over time.