I submitted to every known blog directory when I launched my site in June, 2005. It was great for a quick infusion of links, but now that Google is discounting "untrusted" links, (You can define that any way you want.) I don't think they pass value.
The only other reason to submit to blog directories (or to acquire any other link) is for the potential traffic. I've reviewed my logfiles religiously for 18 months and have only rec'd a smattering of traffic over time.
I've focused on writing for my audience, linking to complementary sites, and adding a profile at www.mybloglog.com
so that other bloggers can find out about me. Another advantage to MyBlogLog is that it shows the outgoing links your visitors clicked on, which gives you a sense of what your readers value.
Since my blog is not a money-making site, I determine my success based on page loads, which continue to rise and validates my presence in the blogsphere.