Elaine asked if I would post on what I know about self-publishing as it seems going the traditional way is often a long hard road.
I've been involved with many authors of self-published books. You can find a few of their covers posted on my blog. Probably the most successful one so far that I'm aware of is the one published by Xulon Press --Women of Passions. Jan and Jeanice have worked hard on their marketing to get their book noticed. I think that's where the success comes into play if you self-publish. Their book even won an award in a category of books published traditionally.
I also have a good friend who published her own book but had another advantage most don't. She owns a huge Christian bookstore and has contacts in the marketing industry so she was able to get a picture and blurb about her book into millions of homes.
I've also know writers who published their own only because they wanted to give it as a gift to family and friends and were happy for that possibility.
I really feel that motive comes into play with both possibilities. If you are looking to get your book out there in more places and bookstores and a bigger realm, I would keep trying to find an agent and sell it that way. If the market isn't taking on what you want to write --for example I read where Chick Lit fiction isn't being taken on right now--then write something that readers will buy or go the route and selfpublish.
As a former Christian bookstore owner, I had dozens of people try to sell me their book to put in the store.I had to turn down most all of them. For one main reason--NOT that their book wasn't any good--but most buyers bought what they saw in ads or were being pushed by the big publishers. Bottom line, I had only so much room for books and they needed to sell to make profit for overhead. So I bought what I thought would sell.
That sounds harsh but I don't mean it to be. If your motive is to have a book in print and you think you have a sound marketing plan, then I would consider self-publishing. If you don't have enough of a platform, audience or reasonable way to sell--then rethink the plan again.
Your book will be advertised on Amazon etc. with many self publishers, but having it there means you have to point people to it. How will you? Do you have a customer base already?
Finally, the choice is the author's. Success stories and failures exist in both realms. Whatever way is chosen, work to get the reader to find you. As I said in an earlier post about blogging, it isn't like the movie--"If you build it, they will come."