From what I have heard about self-publishing, it can be lucrative if you are willing to promote the book yourself. Which is hard, and may not give as big a payoff for you effort. Not to mention that you have to front the money to have the book published, and you might not be able to pull a profit. On the other hand, those who are successful may be picked up by a publisher and will find more success down that route. As in everything, there are nay-sayers and advocates.