In fairness, I should start by saying that we had unusually hot weather during our June trip to Lisbon (hovering around 38 Celsius, 100 Fahrenheit during the day). This was problematic because Marta's flat is on the top floor of the building and has no air conditioning. We had to leave halfway through our stay because the heat inside the flat became unbearable. Not the typical experience, but I would still advise anyone to be weary of this when booking a place in Lisbon during the summer months as many of the old buildings are unequipped for the heat.
Aside from that, the flat is very small but that won't be a problem if you don't plan on spending much time inside it. It is in a great location, very close to many bars and restaurants and walking distance to attractions like the elevador santa justa as well as many public transport stops. It also has any bathroom/kitchen necessities you may need. Great value overall, would probably have given it 5 stars had it not been for our a/c problem.