Here's another vote for Deck 4! Those old-fashioned, cushioned deck chairs are REALLY comfortable. I often went to Deck 4 planning to read but wound up just watching the sea & the people walking/running laps or dozing off. This also wound up being a family meeting place--all 8 adults in our group enjoyed relaxing here, so I was almost certain to run into one or two of them every time I stopped by.
I had the "secret" aft verandah all to myself one afternoon. The view was great, but the place smelled like the inside of a McDonald's--fast food odors that I assume came from Topsiders just 2 decks up. So I didn't stay long. Also, the door to this area is locked at 11 pm each night. (I can't remember what time in the morning it's opened, but there's a sign on the door.)