Venice is a small city, and you can pretty much cover it entirely on foot. Martina's place is great as it is close to the train station, making arrival and departure very easy.
The apartment is small but the rooms are large. For someone who was out sightseeing for most of the day, I found it to be adequate. It was clean, the bed was comfortable, and the hot shower worked.
The heating was less than desirable though. And the door to the room I stayed in really needs to be fixed - it cannot be closed without using a considerable force (basically slamming it shut).