After overcoming our worries about party-ships, we had cruised with Carnival in Feb to Mexico, and were very impressed.
The Fantasy is an older ship and is less fancy than their Splendor (where we were spoiled with a Tandoori grill), but the people on board made up for it all.
It seems most were locals from the SC or NC areas, polite and friendly - you know you're in the South!
Freeport was great - a cabby took us to a -small- public beach; a large area of that beach was unused, belonging to the hotel and would have required a fee. A small stand made delicious cocktails for $5. Later, we ate at a local restaurant around the square which was fantastic. Many fellow tourists had their hair braided (not cheap, $30 for a quarter scalp).
Nassau has changed since I was last there in the mid 90's.. loud, traffic, car exhausts.. we gave up after walking around for a little while.
On the way back, we barely missed hurricane Isaac - funny how they never announce anything on Carnival: they just ran a tape across the sliding doors and said the outdoor areas were "off limits" for now, while the storm was raging.
We had also switched itinerary (went to Freeport first) without any announcements; no bother, just interesting how they handle things.
Overall, Carnival has it down to a science, hardly any waiting/lines on embarkation or deembarkation. We bought a deposit on a future cruise (recommend that) and we'll be back!