Backlink is backlink. Getting free backlink from (even PR 0 directory) on the right category is better from getting no backlink. I recommend you to get as much as backlinks on your website's category. It doesn't matter PR0 or PR8. Off course PR8 is better but PR0 is better then nothing.
We get back links and the site would get a good PR if we have many 'Good' back links. If the directory is active you get traffic from them also. Our website become more popular and to be indexed faster in search engine.
I've occasionally clicked on links while submitting to a directory. Found some pretty nice sites on occasion. I know others that have a few very active directories they like to check out here and there. I wouldn't say you'll get a lot of human hits off it but you would likely get at least some, assuming an active directory.
There are more benefits of directory submission : first thing is you can improve your positions in search engines, you can get more traffic, backlinks and PR.. one way submission is always best because you are getting free link juice from that directories
Directory Submission Increases Your Backlinks, Guarantees Search Engine Indexing, Directory submissions provide increased link popularity.