I have used Expedia for years to book
Disneyland vacations and vacations to other destinations. I have always hesitated to use them for WDW because I read on this board awhile back about people having problems with Expedia calling them at the last minute and saying they could not honor the WDW resort reservation due to lack of availablity. By then it was too late for this person to rebook through Disney as all rooms were gone. I prefer booking through a
travel agent who knows Disney like Small World Travel or
Dreams Unlimited. They do the legwork, check for codes and will even make your priority seatings. Also when you use Expedia you pay the whole thing up front regardless of how far out it is. Expedia's cancellation policy has always been 4 days when I've used them. I have cancelled before and never had any trouble getting them to refund my money in a timely manner. I still use them just not for WDW because Small World has always gotten me a better deal!