This boat was more stable than I would have ever believed. I figured my wife's kayaking days were over after that trip but she said that she was never scared and actually had fun. Cannot get much better than that.
The one area that I had a bit of trouble with is that the seats are closer together than some doubles. This really puts the onus on paddlers being in sync with one another. If you can do this, then you will be fine. Could be more of a challenge with taller paddlers, well, paddlers with longer arms. This is going to be a negative with a double that comes in at 16'6".
The other alternative, to allow more paddling arm room is the Carolina Perception Tandem, but then the stern seat is so far back, it rides with the bow way up with different weight paddlers.
The Polarity also shines as a kayak for you and your child! It is very easy to control and paddle the boat from the stern seat no matter what the bow paddler is doing. This, combined with the weight savings of a shorter tandem, make this boat very easy to handle. I can lug it around by myself without too much problem (sure, I do this for a living, but you get the point. There aren't many other doubles that you can put up on a roof rack by yourself if you know what you are doing).
My rating of an 8 is really an average rating for the boat. The rating moves up if you are buying the boat for the right proposes... and down if you know you and your partner cannot paddle in sync! Thought we were going to have one divorce out on the ocean over that one time too!