The big issue with Expedia (or any other OTA) is service recovery when an irregularity occurs. Buck-passing may ensue; the airline call tell you to go deal with the agency that sold you the ticket, and the agency -- if you can get hold of them -- may do everything possible to squirm out of helping you, and tell you to deal with the airline. Not the quandary you want to be in when you're at the airport and the clock is ticking. (Expedia is probably the best of the lot -- God protect me from Priceline/Hotwire ever again -- but even Expedia is not exactly known for being responsive / supportive in crisis situations.) I do book OTA tickets occasionally when certain weird multi-airline itineraries are irresistible, but always with a sinking feeling in my stomach that is absent when I deal directly with the airlines.