The Emerald was everything we hoped it would be. Prior cruises on Princess included the Coral to Alaska, Sapphire to Mexico, and the Grand to Western Caribbean.
The Emerald incorporates changes that prior Princess cruisers really appreciate: bigger gym, doors that open automatically in heavy winds, an alternative dining buffet at the rear of the ship (Caribe Cafe), and the Sanctuary.
I don't want to spread the word too much on the Sanctuary, but my wife would kill to have that again. It is at the front of the ship and there are no kids, attendant service is full-time, comfy lounge chairs, Bose headphones with free Mp3 players, massage tables in private tents... You get the picture. It is an oasis away from the chaos of the main pools on any ship. It is right above the Lotus Spa at the front of the ship. There is a charge but it is worth every penny.