Just got back from the Mariner. This was our first RCL cruise and would happily sign on for more. The ship is in good shape and the crew were wonderful.
Even though the cruise was based out of Rome and Americans were a minority, the food, activities and general operations were designed for the American market.
If you want a "European" style cruise, you won't find it.
Good location between the elevator banks. Being on the sixth deck was no problem.