We just finished a 12 day Grand Mediterranean cruise on the Norwegian Spirit. We've cruised seven times before, and this was just a fantastic experience. This comes from the viewpoint that I am not a cruise fanatic. I prefer to travel on my own, spend multiple days or weeks in one location, and figure out logistics by myself. So all-inclusive tours aren't my thing. But if they were, this would be the way to go.
The Norwegian Spirit was built around 1998 and refurbished in 2011. It is not a "mega-ship" in the 4000 passenger range, but a mid-range 2000 passenger ship. This is a personal preference, but I find the smaller ship has a more intimate feel to it, and on a Grand Mediterranean cruise, you're spending most of your time touring ports of call (or should be), rather than using ship's amenities. Refurbishment was excellent quality.
The ship layout is typical. We have sailed on Carnival, Royal Caribbean and Norwegian, and there is a fairly standard ship design. All have open atria which extend upwards from the main entrance (in this case deck 7) deck to the top deck and a two-deck "main atrium area" with a double grand staircase connecting the two decks. Buffet dining is on the pool deck, main dining rooms (2) are on deck 5 mid ship and aft. Two-deck theater aft and numerous lounges, restaurants and meeting rooms.