Mariner of the Seas is a lovely ship. It was very clean and altho it could use some TLC in some areas there wasn't any one thing that was "horrible". The crew was great! There is a lot to do on the ship, the dining venues are plentiful.
Aruba- Took the free trolley to downtown. It is a nice ride to the downtown shopping area. Watch the time because the trolley stops running around 4p or so and you will need to walk or take a taxi back to the pier.
Curacao- Very walkable port. They have renovated the old RIF Fort into a nice shopping and dining area. When you walk through the fort you can easily walk to downtown and see the famous floating bridge. It's a nice walk across the bridge into the downtown area with plentful shopping and dining options. We stopped for a cold drink and a snack at the Iguana Bar before returning to the ship. The bridge swings open to allow for ship traffic on the channel. When it opens it is usually about 30 minutes or more before it closes again.