We spent in this apartment 3 days, during a very troubled period for Venice (the flood they suffered in November). Even in a difficult situation for the city, Graziana and Damiano have been just perfect.
First of all, given the conditions of the weather and trasportation, they immediately offered to send us a private water taxi instead of taking the normal public service. Secondly, they provided us with all the materials (water-proof boots for instance), informations and tips to make our journey just perfect. Finally, they have been always proactive and quick in answering us about random recommendations around the city.
Result, our staying in their apartment has been just perfect, one of the best Airbnb experiences I have ever had.
Position of the house: it's 15 minutes far by walk from San Marco square, through a very pleasant and nice walk (you will be able to see the Venice bay from their house till getting in the very center). Restaurants, bars and other cozy places are all around the area. The area, Giardini, is a typical Venetian neighbour full of locals with the advantage of not being assaulted by tourists, but still close to the very center of the city.
Cleanlines and services: just amazing, nothing to say about that
Assistance: as said, top level
Absolutely recommended.