Stayed with my mother (65) and a friend for our three day stay in Venice. It was perfect! Very central location. Easy to get to from the airport, using the water bus and then only a short walk from the water bus stop. The office is a 3 minute walk from the apartment, and they were there waiting for us to show us exactly where to go. They also let us leave our bags in the office after we checked out of the apartment, so we could keep exploring Venice!
The apartment itself was clean, and had all the amenities you could want! Even better - it was on the ground floor - so no stairs to struggle with! It felt perfectly safe as all the windows had shutters/bars.
I would definitely recommend to anyone. Especially if you're travelling with someone who might have difficulty with stairs/travelling long distances with luggage.