Getting just one link will get your PR. The question that you should be asking is: "Are rankings being achieved with directory listing services"?
The answers? No. I like to use those services to kick-start my link building process, just to get the site's indexed and some of the time they do poorly at that.
There are only really a few good directories that you should submit to. I only really submit to 10 now and then work on getting partnerships with other sites. Calling people on the phone for link exchanges works wonders.
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