This was a question recently asked to the Google Webmaster Team and Mr Google himself, Matt Cutts, answered in a short video below.

Matt mentions that the DMOZ directory is showing its age, however it should still be considered a valuable SEO source.

In regards to ranking, a website gets no special reward/ranking boost from being in DMOZ. A link from DMOZ is worth the same as a link from anywhere else; its just that the DMOZ directory tends to have a higher page rank. So a link from DMOZ could carry a little more page rank for your site, just like a link from any other highly reputable sources.

Apart from ranking, Google actually uses the DMOZ directory for computing snippets. If you block a page on your website with robots.txt then Google cant crawl that page. So instead they will look at the listing in DMOZ. If the listing mentions what the particular page is about, then Google will use this information.

Finally, Matt says that due to its age, Google are always testing assumptions when using DMOZ.

There are other ranking factors that carry a lot more weight, so you should concentrate your efforts on these.