I booked a guaranteed cabin because there were not many choice left. It was about the same price as a regular cabin. Two weeks before my cruise, I received my cabin assignment which showed two cabins. I called by MSC cruise agent and he confirmed that we we have to change cabins right in the middle of our cruise. This is because people get on and off at every port and MSC uses guaranteed cabins to keep every cabin full at all times. I asked him if we could have the open cabin (in the same category) and he said MSC would have to approve it. But they would not. When we got on, the check-in person said we could stay in the first cabin for our entire cruise. But three days into the cruise, a form letter was left on my bed reminding me that I would have to move. The people at the reception desk said it was "standard procedure" and common for people to change cabins in the middle of their cruise. So we had to pack all our things and leave our luggage in the hall taking our valuables with us for the day's excursion. When we re-boarded, we had to get new cards for our cabin and no one could understand why we didn't like changing cabins.
The good parts - The ship is beautiful, the workers are friendly, and everyone speaks a passable English. None of the billed gratuity goes to them so if you want to leave a tip, it is best to leave it on the table and/or cabin on the last day. The cabin was nice with storage space but only has one outlet available. So you may want to bring an electrical strip. Our cruise rate was reasonable but you often get what you pay for.
The not so good parts - From previous reviews, I knew the food would not be fancy but their buffet makes an inexpensive family buffet look like a 5 star restaurant. Salad, bread, apples, and oranges were always available but their cuts of meat range from pig necks to rolled and pressed turkey. Water is available at the buffet but a sign says not to fill water bottles for hygiene reasons. The buffet was always crowded even at off times and it could be difficult to find a table. In the main dining room, we had to buy a plastic bottle of water each evening, so much for being green. Our table mates, who had been on several other MSC cruises, said the food and activities had sharply declined. Even their shrimp was fishy but no one got sick.
There is no advantage to the web check-in since each person is given a group number when they arrive. Activities during "at sea" days were few. One day they had shirt painting but there was only room for 7 people on a ship of over 3500. I noticed that people didn't participate very much in activities that were extra money. The casino had few people gambling, the spa was mostly empty, and not too many people were drinking alcohol. We took three MSC excursions and the buses were only 1/3 to 1/2 full even though they combined the languages (e.g., English and German). Internet cost 12 euros an hour, is slow, and the mostly empty Cyber Cafe is even more expensive. Given the large cutbacks and lack of spending with the other cruisers, it makes me wonder if MSC is financially sound. Anyway, don't book a guaranteed cabin in ANY category unless you want to move in the middle of your cruise.