Our experience at Leonardo's had both good and bad aspects.
On one hand the location was excellent, only a short water bus ride from Santa Lucia and easy access to all of the surrounding islands for convenient day trips, not to mention away from most tourista. Leonardo was also EXTREMELY helpful in locating the apartment, providing tips for places to eat and drink (which helped us stay away from the tourist floods near the popular areas) and staying in touch throughout our stay if we needed anything.
As for the apartment itself, the entry way was undergoing some major renovations, however they didn't bother us much in the apartment itself on the upper floor. The apartment had all the essentials but needed some upkeep and repair. The fan in our room was broken and we so we used the one in the other occupied room, but this became an issue when the room was occupied the next day and we had to abandon it and sleep in some hot conditions. Certain areas of the apartment felt dirty and the sheets/bed had a funny smell.
We very much enjoyed the area and considerate hoat, however the next time we visit Venice we will likely look for a different place to stay.