I loved my cabin room below deck, and the water was so calm I often forgot I was on boat. Fully satisfied with my room, which was clean, cosy and offered a unique view of the water at eye level.
The shared bathroom, however, could be greatly improved. The one below deck was broken in a lot places (loose toilet bowl, stuck shower door, etc.) and it made an atrocious amount of noise when flushing, which made me feel bad for the person in the cabin next to it. Given it was the only bathroom on that deck, It was much better to use the toilets and showers in the deck above, which were more communal. I wish the staff had told us that.
Other than that, value for money and located walking distance from the historic sights of Gamla Stan and all the nightlife in Sodermalm!