I've never booked a Disney trip through Expedia, but I've used them for other trips elsewhere and haven't had any issues with them. If it's cheaper, then book it! The only disadvantage is that you can't get the dining plan, but you're getting the same room. We used Coke reward points to stay at POR last December and got the room for $82 a night. Disney's best rate at that time was about $180 for POR and even the values were about $95 then.