Mariner of the Seas receives high praise for its friendly and hardworking staff, enjoyable entertainment, and a variety of activities, especially for families. Many guests loved the private island CocoCay and found the ship comfortable and well-run. However, some reviews mention that the ship is showing signs of age, with outdated cabins and maintenance issues. Food quality is generally good but inconsistent, with some guests disappointed in the main dining options and allergy accommodations. Crowding in public spaces and extra charges for amenities were also noted as negatives. Overall, the cruise is recommended for its service and fun atmosphere, but there are areas for improvement.