The apartment is surely cute, comfortable and central, just smaller than it looked in the photos \tall people should pay attention to their heads\
If you want some quiet at night, find something far away from Bairro Alto, human rivers of young tourists get drunk around that area every night and it can get quite loud.
The area is very central, just don't expect some authenticity, since it's a super touristic neighbourhood; from there you can move on easily and quite fast to other \ better \ places around the city.
>> The apartment was clean and nice but quite hot \ there are 4 ventilators which is a great feature but the electricity went away twice in the building during the hottest days. At this point it was unbearable to stay in there, I really hope the owners will do something about it.
Conclusion: It's a very cute apartment with a nice terrace and we had a decent stay there, for the same price i think you can find something better and in a more authentic area. Talking about authenticity, this is not some private person renting out the place, it's commercial use and that's getting to be a problem in cities like Lisbon and Berlin. If you want to practice some conscious tourism, look for something else.
https://hbr.org/2016/07/airbnb-is-facing-an-existential-expansion-problem