My goal originally was to get an agent first, but I spotted am opportunity to get a publisher directly and I have no regrets. I have a good contract, considering I'm a first-time author, but I have a friend who works in marketing at a non-fiction publisher who looked over the contract for me before I signed, and I did my homework on the publisher themselves before even submitting. An agent will look after your interests in that regard for you.
It all comes down to what you want. I wanted traditional publishing because I want a professional editor to work with me to make my book the best it can be, and while I'm aware that ebooks are a hugely important side of the industry, I wanted to see physical copies of my books on shelves. I just don't have the funds to do all that on my own.
While you can self-publish very quickly, you need to remember that you're entirely on your own as regards marketing. Even Amanda Hocking has signed on with a publisher now because the work she had to do to market herself and her books was taking so much time away from her actual writing. Now, there is always a need for an author, especially a new author, to promote themselves as much as they can on their own, it will be that much easier with an agent or publisher helping you.
In general, my advice would be to seek traditional publishing, and an agent, as your first option. Sure, you'll earn a lower percentage per book sold than if you self-publish, but your odds of actually getting copies sold, and of your book being at a standard that will attract readers to the all-important second book, are usually higher with a publisher.
While you're doing that, start building your online platform. Start a blog, get on Twitter. Post on Absolute Write, join Goodreads. Look up Kristen Lamb on Twitter and her blog. She has a wealth of advice on using social media to promote yourself.
