Directory listing will help, depending on which ones you choose. I dont think they are as important these days unless they are very relevant to the site creating the listing. I think good directories have their place within the SEO project cycle, but there are very few that add real value.
Agreed.... they would only get you there on very non-comptetitive terms.. which are unlikely to bring traffic.
I think it can when you use your targeted keyword. But it is very isolated case. It's a big difference when you also apply the proper onpage-and off-page optimization.
Sometimes I don't rely on just building links by submission because directories may have higher rank than your site using your keyword.
u can receive SERPS with no major links at all.... aslong as ur content is recognised. Directories are mainly used for basic unqualitised linking... rnt they???