We stayed for 7 days in Elsa's flat and here are the positives and negatives of our experience:
Positive points:
The location was very good, mainly in walking distance of all nice places (Alfama, city centre, Chiado, Graca, etc ) the bed was nice and comfortable, the sheets and towels were clean, there were enough blankets, the heater was working well, the box with the books, maps and flyers for visiting Lisbon provided some good information, the kitchen stove and the toaster also worked just fine. There were enough cuttlery and plates. Also the communication with Elsa and Francisco was nice and the check-in experience was very friendly. The Wifi was pretty decent, except in the bedroom.
Negative points:

- the cleanliness of the flat (as we found some hair from previous guests on the ground and in the bathroom)
- the smell of humidity in the kitchen cupboard, which made us want to avoid opening the cupboard to fetch some cooking stuff and plates
This is especially a pity as the cleaning fee for the flat is quite high 70€, considering its small size.
In addition the hot water supply is just enough for 2 people to have a 10 minute shower, which is ok but can be a little short, especially for girls... Also the water did not flow out of the shower as it should have which lead to the shower being full of water after a few minutes of showering.
The sofa/bed in the living room is quite uncomfortable/ very soft. As it was raining, we stayed a bit more inside and the sofa is really not made for sitting on it for a long time.
Also the pillows were extremely soft, which is not a great support for the neck, even though I guess everyone has his or her own preferences.
So all in all, the stay was OK, but we would have expected a little bit more, especially considering the high cleaning fees. I hope these things will be improved in the future to achieve a 5 star rating for the next guests.