We stayed in Nuno's apartment for a five-day trip to Lisbon. The location is perfect for exploring the city. Many tourist attractions are in walking distance and we loved exploring the area around the apartment, where you can find lovely bakeries and many good restaurants. Bus stations are a 2-minute walk away, from where you can pretty much go anywhere in the city. In general the apartment and alleys around the apartment are very quiet.
The apartment is quite small, but when you are out and about all day long I'm not sure that really matters. Bathroom/shower is very small, but again manageable, however it might prove tricky if you have some mobility issues. The apartment is not accessible by car (you will meet host at prearranged spot and walk to the apartment together) and you will need to climb steep and small steps to enter the apartment.
Biggest plus about Nuno's apartment: host is incredibly responsive and helpful, answering all questions, even arranging a 3 am taxi for us.