We purchased some Disney Quest and Sea World passes through Ticketmania. Within about 12 hours, I came across a tip on this website which would allow us to get the Sea World tickets for a lower price. We called Ticketmania and they agreed to cancel out our order and just sell us the Disney Quest tickets-- very nice of them and in my opinion, something they were in no way obligated to do. Now, we are scheduled to pick up our tickets at our hotel on Tuesday, so we don't actually have the DQ tickets in hand yet, but so far I'd say these folks are gems.
PS I have checked my credit card bill and we were charged the full amount for all the tickets and then credited back the amount for the Sea World tickets. So the charge had actually gone through and they still were willing to make the change!
Two thumbs up on Ticketmania!
Beatnik