I've never made it to MCO in time for a 10:00am flight. We generally get to the airport at around 9:30 or so. Like Dave said, that might be cutting it close. The latest I've been there is 10:30, but that was shortly after 9/11/01, when the new "security" was in place (no luggage check at port, no curbside check at the airport, etc.).
We always take the
DCL buses, so you can adjust for that. I would think you could get there a bit more quickly with say, a towncar, but I don't know that you could be assured of making a 10:00am flight.
On rare occasions, the ship is late getting in to port. On all of our cruises, we've been off the ship between 7:30 and 8:00 am. You then have to claim your luggage and file past the Customs agent, which can slow you down a bit.
My personal feeling is that I wouldn't book a flight eariler than 11:30 AM. We usually get one for 12:30ish, especially if we have DCL book our air. Of course, I err on the side of caution, as I don't particularly mind waiting in an airport (as opposed to stressing about missing a plane). I'd say, practically speaking, anything after 11:00
should be OK.