Backlinks are not judged. Directories are crawled by the search engines and if your link is there it becomes a backlink.
A backlink is a backlink - however, nobody knows if Google applies the same weight to directory backlinks or not. I personally doubt it.
What matters is if the directory is related to your site. Links from related pages count more. So niche directories will carry more weight than general directories.
HI I use Google Alert to monitor some keywords and phrases and domain names... and I have noticed... when people submit a paid listing to my directory within 24 hours or less I get an email from google alert telling me google found that listing.. So yes I think directories work... but it happens for paid listings only... as they do not have the nofollow tag... Tom
Google do place more weight on backlinks from special sites, and if the backlink is from dmoz, I don't think google will place less weight.