For us, half the fun is actually planning everything, so we do it all ourselves. We book most everything through the Disney site, except for airfare and car rental, which we book directly with the airline/car rental place. We usually use an airfare comparison site to find some good airfares, and then hone in on the fares with the respective carrier.
We do have some friends that are going next summer, though, for the first time (family of 5). For that purpose, I told them about a great local travel agent in our town. I knew she was very good with Disney, so they were able to sit down and have things explained and she really worked with them. I think this is a great service for people who just don't know where to start.