We went on the holiday (Dec 24-31) cruise on the Oasis with my 3 boys (18-23yo) and my parents in their 80's. It was wonderful.
The best part was the crew. Everyone we passed in the hall or anyone we had contact with had a smile on their face. They made eye contact, said hello and asked how they could help. What wonderful training RCI has for their staff!
The ship is big and we had 6200 passengers on board but honestly we never really felt crowded. There are so many venues to hang out and people do so many different things that there are no crowds. Even the check in at the terminal was incredibly efficient. (btw, we got on at 11am. Don't believe the 2pm arrival time. You can start your vacation 3 hours earlier!).