We have been on several cruise lines and understand that Carnival is a great value. But when the price is low (as this cruise was), not everything can be outstanding.
Here is a tip for anyone sailing from Barcelona - the terminal is too far from town to walk! Take a taxi and have some sympathy for the people you will pass along the way pulling their suitcases up and over the bridge to the terminal.
My second tip is about chapels and churches. You will see plenty of them (Vatican, Pisa, etc.). Schedule your excursions accordingly.