We (three adults) spent a nice weekend in Maddalena's Venice apartment. Communication before arrival was very fast, precise, and complete with several pdf files of information sent.
The apartment is essentially a 4 story row home with a single room located on each floor. The ground floor houses the entrance and well equipped kitchen with comfortable space for 4, second floor is the living room which doubles as one of the advertised bed rooms (note that everyone will be walking through this room on the way up or down). Third floor bath with the bathtub being located under the stairs going up. Since this forms a triangular ceiling above the bath tub, it is another reason besides the wall concerns listed why showers are extremely impractical. There were no shower curtains, but a set of towels per person was laid out. Also on the third floor is a children's room with two bunk beds for children. The top (4th) floor is essentially the attic of the house with the roof defining the sloped ceiling. A small window provides light and air. Mattresses for two are placed on the floor and two lamps complete the furnishings of this floor.
During our stay Maddalena quickly resolved a problem when we discovered that the cleaning service had left a full load of wet laundry in the washing machine.
Overall we enjoyed the quiet neighborhood and central location of the apartment with 10-15 minute walks to almost everything. It made for a good base station for exploring Venice. When we stayed here at the end of May, day time highs were in the mid 20 degree Celsius and the bedroom in the attic was comfortable and not too warm during the night.
One important item to stress for new visitors is that Venice is a maze (made easier by Google Maps) and transportation by vaporetto and walking will take time. Allow at least 45 minutes to get from the entrance of Venice (either Tronchetto car park or the train station) to the apartment or your host (in our case a friend of Maddalena) will be waiting a very long time for you.
One other thing to note: Venice is a walking town with lots of bridges. Lugging large suitcases to any apartment (including this one) should be avoided. If you do decide to bring large pieces of luggage, be aware that this apartment consists of 4 floors of narrow stairways. You will very likely end up leaving all luggage stacked in the ground floor kitchen.