Just my opinion but I think they are a waste of time these days as far as gain search engine rankings. There are many other better ways to get quality backlinks. Consider article submissions and Press Releases
It isn't really a case of being nothing wrong with it, it's more the time factor involved. Why waste potentially weeks of time submitting to crappy directories if you get barely any benefit? If it takes you much longer to find good quality directories, but there's fewer of them, then it's definitely the better option in my opinion.