First time cruiser chose Crown Princess for the itinerary - Athens to Barcelona July 7-14.
First, the good:
Our state room was fantastic.
14th Deck Riviera Balcony, way up toward the front of the ship. Gorgeous room, full closet, loads of storage, lots of lighting, great ventilation, mini-fridge, one electric outlet on the desk, one in the bathroom, plenty of water pressure, powerful heating/cooling system. We loved it.
If you are boarding at Piraeus, and the ship is docked at Berth 12, you need to know that it isn't a plausible walk from the subway. Better to take a cab.
This was my favorite port. Hiking up 100+stories to the castle is worth it, and a great accomplishment. The touristy town of Kotor is a delight with narrow streets and many shops. We found a Montenegran restaurant off the beaten path, which was very good and had WiFi: Cesarica.
Sagrada Familia is not to be missed, and if you don't have a tour then you'll need to buy your tickets online months in advance because they sell out. But don't neglect Gaudi's other work -- Casa Batllo especially, but also La Pedrera and Park Guell, to get a richer understanding of what Gaudi was up to (for example, his other works aren't religious at all).