As others have said, the family pool deck is the only part that ever really feels crowded to me. Cabanas can be crazy, especially on embarkation day, but other than that, I've never felt like I was overly crowded. Pirate night is nuts during the show, but I head up to Currents to watch the fireworks, so I'm not too hemmed in.
Then again, I avoid the family pool deck like the plague if I can help it specifically because of the chaos and noise inherent to that many people in one place. I tend to use deck 10 as a corridor from the forward elevators to the aft elevators, staying away from midship as much as I can.