1. Directories are for backlinks , traffic will be very minimal sometimes . Directories are good for new sites just starting out and needing some backlink boost. For your 1-yr-old and PR6 site, I would say it’ll benefit u much more if u put the time to gaining natural backlinks.
Directory Submission is even better, just pay someone to do the directory submission. 
2. Directories can provide you natural and permanent one way linking. but for that directories should have at least PR. If you are submitting to site having no PR. OR Even not indexed by Google than that will worthless sometimes but it completely depends on Niche.
It might help you a little too if the keywords in the title of the link you are submitting rise in rank for your site.
3. Submitting to every directory you come across isn’t considered essential, but it doesn’t take 5 minutes to go through the submission procedure, and it means you will end up with extra backlinks at the end of the day.
Directories can give you HUGE traffic. The traffic is not direct from them but it will boost you in SERP results which will give you the traffic.
Directories > Search Engines > SERPS > Traffic > $$$$
4. Another option is also there if you are not interested in Directory submission .You can also do social bookmarks, relevant blog links,forum links and various other metrics
that can help raise your search engine ranking… BUT Directories are the easiest
and fastest way off getting attention to your website from the SEs as they are indexed
regularly. Providing you submitted to that directories “proper” category its a positive vote
that your site is actually what it is and that it was reviewed by a human. On rare occasion
a directory can also send you some traffic from its visitors that are looking for specific info.
I hope this answers the question at hand… 
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