If you're buying a house, it's so important to have representation. If you go out on your own and only talk to the agent who has listed the house that you're interested in, that agent is already representing someone else - the seller. If the seller agrees, the agent can represent you also but make sure that the agent is comfortable working as a dual agent because it's tricky.
If you have a buyer's agent, not only does it not cost you anything, but he or she can pull up comparables on whatever house you're interested in and make sure that you will not overpay. The buyer's agent can negotiate for you and try to get you the best possible deal.