Our family of 5 (2 adults, 3 kids) stayed here in September 2018. It was our first time in Venice. When we arrived into the Venice Train Station we followed Marta's instructions and got in line for the water taxi. We waited 1.5 hours before getting on, then it made many stops on it's way to the island of Lido. There were pickpockets we witnessed on the water taxi.
Once we got off at Lido we found the bus stop and waited for the next bus. We rode that to the end of the road and then walked up the street to the alley where the apartment is located on the upper floor. We had 5 large backpacks and this was a challenge. I think it would be tough with suitcases.
We retrieved the key as Marta instructed, but there was a little paper note telling us to open the blue door. The key did not work. We emailed and texted Marta and did not hear back for about 30 minutes. We were trying to get to mass that evening at San Marco, so we walked back to the bus stop, rode the bus again, waited for the water taxi again, and had to attend mass with our luggage.
When we heard back from Marta she said the paper was wrong, the door was brown. We did the entire transportation routine a third time and got in.
Once we cleared the key problem, the unit worked out fine. It was as described and worked fine for us. It had nice spacious bedrooms and a functional kitchen. The shower is small though.
If we come back to Venice we would likely book a unit closer to the city as transporting back and forth took a fair amount of effort and time. If you are savvy with public transportation and patient with lines, this might not be an issue for you.
We never met Marta during the course of our time here.