I had a site for 6 months without traffic or PR And when submitted to 600 guaranteed listings i got PR1 and high traffic I believe directories works nice for me
In my opinion, directories would be in the first place as free back links source. It all depends to which directories you submit, as any other websites, there are quality web sites and non quality web sites and directories are the same, if you submit to quality web directories then it will help your web site gain quality back links and rank better, but if you submit to non quality web directories, then don't expect too mush.