My experiences in doing air thru
DCL have been a general disaster on domestic flights. They are always more costly than booking on our own + adding transfers. They pick flights that no sane person would. For instance, we had a direct flight to Orlando that departed at 8:30. But DCL wouldn't use that direct flight--they would book us on a connector thru Atlanta that departed at 6 or 7 (there were 2 of them) and arriving hours later than the direct flight.
The other thing is that I feel very strongly about flying in the day before if at all possible--even if that means a late flight after work/school. DCL will only do that if you stay at one of the hotels they choose at their price; even if I want to stay at the Hyatt MCO, I can usually book it cheaper on my own than thru Disney! And I can always choose other hotels cheaper.
The only good things about DCL air are that if you book your insurance thru Disney, it will cover the air also AND if their air arrangements don't get you to the port on time, they are responsible for getting you to the next port of call or whatever to salvage as much of your vacation as possible. Yes, they have held the ship for a SHORT time for someone who had a flight disaster, but there is no promise that this will happen.