The very significant problem for many, unless you are extremely close with the other couple, is that you have only one bathroom. The people in the main sleeping area must pass through the sitting area with the pull out bed to get to the toilet at night, too. Dressing for dinner can become a nightmare, in fact dressing at any time can become a problem undertaking. It really doesn't work at all.
A better suggestion... one couple take a mini suite or regular veranda cabin and the other take a nearby inexpensive inside and share the pleasure of the balcony during the day. I'd think long and hard about two adult couples sharing a cabin.