We're in the process of building a house and we did use an architect. There are advantages to this--you get to tell the architect what you want in your house, any details, including solar panel or any energy saving concerns you have. You get to specifiy and he will do as you want and sometimes, he will even suggest things you overlook. You get to brainstorm ideas with him and that will help to produce a house that you always wanted.
On the other hand, it can get expensive as they charge by the hours they put in. Sometimes, when you want to change certain things after he has drawn up the plan, he charges extra too.
I've heard of others who use already drawn plans from online sites. It's cheaper.