I've cruised with Crystal, Princess, Norwegian, and Holland America, and without a doubt, my experience with MSC is the worst. Although the fare was lower than expected, transatlantic from Barcelona to Barbados, the "nickel and dime" experience on board, coupled with frequent billing errors, poorly organized shore tours, and poorly managed buffet staff, made the experience unforgettably poor. I found it interesting that most of the on board guests expressed similar dissatisfaction with MSC and would not be taking another cruise.
MSC is obviously managed by Accountants, with the goal of maximizing on-board revenues without regard to customer satisfaction. Paying US$3 for a small bottle of unknown water, $5 for coffee after dessert in the main dining room, are two simple examples of everything is for sale, nothing included.
The shore tours were poorly organized, with every tour departing late, thereby missing valuable on-shore time. On the tour to the Pope's Palace in Avignon, our tour guide actually last an older gentleman! Couldn't find him, and we departed without the ill fated man. I never found out what happened to him! In addition, the tour guides were difficult to hear, as they had no mic/earpiece sets, and so with most tours I hiked out on my own while reading Wikipedia.