I've done crusies both ways. Latest arrived MCO at 12:00 and using Quicksilver, going straight to the ship. When I booked the other day, I was told that the last transfer was 1:30 which would get you there about 2:30. They will wait to the transfer but not private transportation.
Supposed to be onboard by 3:00. Life boat drill is about 4:00 at your muster station.
I'd be worried about anything but direct flights. More chances for late plane or baggage transfer problems. After our problem last year getting to Seattle for Alaska cruise, DW is insisting on going down evening before for our Sept cruise on the Magic.
HIGHLY recommend travel insurance. Waste of money if you don't need it, but when they told me last year that I couldn't get into Seatle until AFTER the ship was schuduled to leave, I became a lifelong believer, at least for crui$e$.

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Richard Carmichael, Chesapeake VA
DVC Member BLT, VGC & SSR
2009 SSR(x2), AKV, BWV, BLT(x2), VB, DCL Magic; 2008-SSR, WLV, OKW YC; 2007-YC, GF: DCL Wonder; 2006-SSR, SoG, Poly; 2005- Poly (x2), Orange Lake; 1999-Courtyard LB; Disney Inn (RIP - now SoG) '90, '88, '86
Make-A-Wish Volunteer www.wish.org My Wish - no Wish Kids to send to see THE Mouse. 
2nd Fav Org -
Give Kids The World Village www.gktw.org