I started off using one... One from dw.com, but she kept telling that she couldn't get pricing for Canadians until a certain time which was being pushed out further and further (July of this year was going to be time she going to be able to get prices). Anyways, I stopped using them then went AMA, but they would only give me prices for Air Canada, and the pricing they were giving me were $2000 more than other packages I could find.
So I basically I gave people quotes (gave the websites, and phone numbers as well) from Air Canada, American Airlines, Book.com, and Continential. Let them pick there own packages with who they wanted to travel with.
It worked better for us, people saved money, and never really have any problems.