My friend and I stayed at Sofia's apartment only for a short night - we booked her place because we needed to be in Lisboa early to catch a plane. When discovering the apartment, however, we felt quite sad we would not stay for a longer time! The flat is very big, luminous, furnished with a great taste and extra clean, basically matching professional standards - the kind of place from which most hotels should take inspiration. In addition, Sofia is a totally ideal host - communication with her to setup our arrival and to organize our departure was seamless, and she made us feel welcomed through many little details (providing some tea, crackers and jam provided for our breakfast, remaining available anytime, etc.).
Since we did not stay more than one night I cannot comment on the location of the flat for people willing to explore the city, but if you care about being able to reach the airport easily this is a perfect solution (less than 10min away by taxi!).
I would not only strongly recommend Sofia's apartment, but totally hope to come back for a longer stay!