My husband and I liked the apartment very much, although it literally had four flights of stairs. The neighborhood was definitely a local area, and it was quiet and away from the heavily-traveled tourist areas. The furnishings were nice and the apartment was in very good condition.
I originally had booked this for four people - my husband and I, his mother, and our friend. What we didn't realize until we arrived is that there really are only two real bedrooms, and the apartment is more geared toward two couples using those bedrooms. (It is possible that I missed something in the description when I booked the apartment.) This is especially true during the summer, when the temperatures soar. The third bedroom is actually a loft, with no A/C wall unit, so it was stifling hot, even when we opened the windows to get some cross-ventilation. I think it eventually cooled down during the night, but it would be hard to sleep there. Our friend ended up sleeping at another apartment because the heat would have been too uncomfortable.
The apartment is 1600 meters from San Marco, NOT 800 meters. This turned into a major challenge for us, as my 76 year-old mother-in-law does not walk well, especially in the severe heat and humidity that we experienced during our visit to Venice. Between the stairs (and you can't reach a bedroom without climbing at least one flight of stairs) and the distance to the main attractions, I would not recommend staying here if you have elderly family members or very young children.
One other bit of information: if you are coming from Marco Polo Airport, you cannot get to the Giardini ferry stop without taking a water taxi. The airport ferries do not stop there. You have to get off at Arsenale, turn right, go over the bridge, and then start making your way up Via Guiseppe Garibaldi, which will be on your left. There are tons of wonderful little restaurants along the way, and you can't go wrong eating or drinking at any of them.
I think we'd consider staying there again, but only if we were alone or with another couple that didn't might a lot of walking.