As a test I submitted one of my sites to a few directories for a keyword that I thought I'd have NO chance at ranking well for, it was quite some time ago now. I would say that it was about 100 directories altogether.
The site went from #359 to #16 over the course of 6 months (as all the links were discovered by Google) so I would say that was pretty conclusive that directory submissions actually work... So, time went by and I basically forgot about it. I wasn't particularly interested as I already rank well for other terms.
It jogged my memory last month so I decided to submit to another few directories - about 10 of them. Now I am on page 1
It seems that directory submissions are still a good way to help your SERPs, despite what some SEOs might have you believe.
James.