To make it short: I recommend this place for staying several days in Lisbon. But not for more than three guests.
This place has AC, a well eqipped kitchen, some basics so start with and comfy double beds. The flat is very central and many nice places for coffee and food are just around the corner.
During our stay, it was really quiet and peaceful in the neighbourhood.
It also has some downsides as it is in the third floor with very steep stairs. Bringing large suitcases up is no fun, but not impossible.
There's a third double bed in the living room, which we didn't use. Since the living room is very bright and has no windows blinds, it's not the perfect place to spend the night.
Communication with Gaetano was easy and responds came quickly.