Sergio's place was great, and his hospitality and communication was excellent. I thought the place was wonderful as there were many fresh grocery stores close by, as well as bus stops. It was also very quiet with air conditioning. It is also a charming, quaint flat on the inside.
Some things others should be aware of: 1) it is at the top of the building - 3 flights up. It didn't bother me but you should know you will be walking up. 2) the closest tourist attractions would be the Belem area, Coach Museum, and the Jeronimo Monastery, and that was about a 15 minute walk. The Alfama city center is about a 45 minute walk, but very easily accessible via bus. The bus stop is around the corner and there are many of them (take them to Cais Sodre). There was also very easy access to this place via Uber and taxi. Both of those were about 6-7 euros from Praco do Comercio.