Only expect what you put into them, submitting to a directory that is standing still does no good. However, directories that are constantly promoted and bring value to their links is a good investment and good for your site.
directory submissions is a good way to promote a site.. they can indeed affect the popularity of your site and they can increase your ranking in search engines. Though directory submissions by themselves are not going to get your site up there... but if done with a few other link building strategies, they're quite effective.
I agree with quickpot. just make few quick submissions with your cup of coffee, it won't make anything bad...