We took the Carnival Liberty, Western Caribbean, out of Miami on March 13 (Spring Break). We are a family of four including kids 16 and 12. For my wife and me this was our 4th cruise (2 on NCL and 1 on Holland), for the kids it was their 2nd (1 on Holland).
Travel to Miami We purchased air from Carnival since we didn't think we could do better on the price given that it was spring break. Carnival put us on a direct flight into Miami arriving at 2:15 with a nominal 4:00 ship departure, later than we would have wanted but all indications from Carnival were that if we were a little late, they would wait (no guarantees of course). We took a taxi to the port of Miami (fixed fare of $24 plus tip) with no problem at all and were there around 3:00. Having to print out our own luggage tags and staple or tape them on did not impress us.
Embarkation Since we were arriving so late, embarkation was a breeze with no lines to speak of. We were on the ship within 30 minutes or so. I did like that you didn't have to carry your life preserver up on deck for the drill though some may want to try it on if it makes them more comfortable. We left port about 1 hour late.