Expedia has ruined my Christmas vacation by not keeping up to date itineraries and when I instigated a change they confused the backend and I wound up with no seats at all. When I called customer support to fix the issue they were completely unable to help me. Gave me incorrect information and no specific person to follow up with. It is not the policy to even give out direct contacts for fear someone will track them down - RIDICULOUS! I have now spent hours trying to find a solution and am not guaranteed one. I will only work with a reputable travel agent or the airlines directly.
You can still get great fares on airline websites or via a travel agent and even if it is a little more money peace of mind is worth it.
Every agent and supervisor I spoke with had a different story and had no way to validate any actions being taken. Their backend system has several flaws including not logging a correct itineraries.