Where to begin....let me first say that these are my own opinions, obviously, and others may disagree with me on some of these points. I don't intend to insult anyone. Our main intent for this cruise was just to get to the destinations without having to pack and unpack in each city, on a strict budget. My companions and I are in our late 20s to mid 30s, so this may be an entirely different experience for older folk.
Embarking: we were able to drop our bags off at 10am and explore Barcelona a bit before entering the ship, which was nice. Taxis are aplenty at port, though you may have to wait in a long line to go back into the city depending.
Room: we had three girls in an interior room towards the middle of the 7th deck. It was really the perfect location, in the middle of everything. I thought it would bother me not to have a window, but it wound up being fine. I wouldn't have more than three people in a room, though. The bathroom, as you can imagine, is really, really small. The shower is nearly impossible to shave in. But we expected all of this so it wasn't a problem. The TV has very few channels, but if you're not spending a lot of time in your room, this won't come into play much. There are three closets that are a pretty good size and a dresser with three small usable drawers. The beds are high enough to slide a good size suitcase under them.
Pool & Pool Deck: the pools are smaller than we had expected. The one in the back of the ship is the quieter one. The front is where they have a live band or loud music. The back has music playing but more in the background. It's difficult to find a lounger by the pool if you don't get up early, but we had no problem finding one on the 11th or 12th decks no matter what time of day it was.
Food: Horrible. There's no way around that. We heard some people say that it was terrific, and I feel sorry for those people because they haven't been exposed to truly good food. We tried the buffet, the dining room, and the Italian restaurant that requires a fee for each guest ($10). The buffet: the omelet bar, burrito bar, and wok bar were okay, but everything else was awful. Burgers sit there for hours; buns are stale; hotdogs are boiled until they're mush instead of grilled; meat and seafood are overcooked; somehow the salad bar wasn't even that great and that was just straight up veggies and beans. Southern Lights dining room: We were at the youngest table and were served last every night. As a result, almost every entrEe was served cold. Our app plates would sit in front of us for way too long before being cleared away. Desert was nearly always melted by the time it was served. It took over 2 hours every night, which was not necessary in my opinion. Servers have more than one large table, so they are run ragged by the look of things. And each night dinner ends with a man singing Sinatra and the servers getting up on pedestals to dance a "friendship dance". I know cruises can be cheesy but this was waaaay too much for me. Italian restaurant: not great, not terrible. The pasta was cooked well, but it was served luke warm and wasn't great. I don't think it was worth the extra $10.
Entertainment: Danny in the Red Frog is good, but everything else we heard music wise was cheesy to the max. All onboard musicians LOVE Bon Jovi and have a very limited selection of music that they play. We didn't watch any of the comedians or see any of the other shows, so I have no opinion of those.
Service: our room porter was great; waiters at the Red Frog are terrific; other service was alright - not great, not horrible.
People: Most people on the ship were seniors with very few children since school had just started. We were shocked at how rude the majority of the people on the ship were. Pushing and shoving to get into the buffet. No "please" or "thank you" or common courtesy. No manners at all. It got to be really, really annoying by the end of it.
Disembarking: we had no problem. We were allowed to begin disembarking at 5:45am. We left the ship between 7-7:30am and just breezed through. We didn't even have to wait for a taxi.
Buy this book: Seriously, do yourself a favor and pick up Rick Steves' Mediterranean Cruise Ports. It was our bible throughout the entire trip. When you have only hours in a city the size of Rome, you don't have time to mess around. This book gives directions by walking, transit, highlights of the city to hit up, restaurant recommendations, what to do if you miss your ship, etc. I don't know what we would have done without it.
Itinerary: Be prepared for changes in the itinerary. We were told on our first day that Rome was having a transit strike the day we were supposed to be in port, so they had to shuffle things around. As a result, we would no longer be going to Naples, and that Naples was replaced with Marseilles. Many people, including ourselves, were very upset with this. We chose this cruise
specifically for the destinations, and they can just change them on a dime. They said they'd notified us the week before, but they had not. The times you think you'll be in port are also likely to change. I believe Florence was initially supposed to be 7:30am to after 7pm and it wound up being 10:00am to 6pm.
Excursions: In the interest of saving money, my companions and I opted not to do any excursions through Carnival. They are way too overpriced in my opinion, and I am not a patient person. I am also comfortable with public transit. If you do choose to go on them, be prepared to wait on people and not have any say in how you spend your time in cities. Our tablemates told us that no matter the amount of free time they say you'll have, it never winds up being that much time.
Self-transfers into main cities from port: Italian trains are VERY unreliable. Trains get cancelled and break down all the time. Both happened to us in Florence. Do not wait until the last minute to come back, because a cab ride from Rome or Florence back to port is going to run you hundreds of euros. Liverno requires a 1 hour and 20 minute train ride into Florence. We split a cab to the train station. You'll need to make sure that the train you are on is either direct or requires a transfer in Pisa. Be sure to ask this (we almost wound up not transferring, ending up god knows where). Once into Florence you can take a bus to wherever you want to go. Rome requires a 1.5 hour (or less) train ride from Civitavecchia. The train station is within walkable distance from port. Once in Rome, you can take the subway to the Colliseum or Vatican, or wherever you want to go. It's really easy once you figure out what line you need. The book I suggested gives explicit directions that we followed seamlessly. When going back to port, give yourself at least 20 minutes to walk to the platform once in the train station.
Taxis: be sure to ask how much it should cost you if you can, because they will try to rip you off. If it winds up that you need to take a cab back from Rome, I know friends of ours talked a cab driver down to 120 Euro. They'll likely aim for 200.
Theft: be smart with your belongings. Thieves run rampant and they're not all scary looking men. We had someone tell us that a little old woman attempted to jack his wallet.
I hope this helps!