The apartment was in perfect condition, climate controlled and in a pleasant, safe area of the city that was quite well lit. The beds were very comfortable (memory foam) and the owner even went out of their way to add extra beds for our kids. There was a supermarket within a 5 minute walk and easy access to public transportation (and even the zoo!). Parking (on a weekend) was readily available up and down the street, with a full lot across from the apartment.
The only improvement I would suggest is to provide better lighting in the stairway to enter the building. It was a little difficult to find the light switch in the dark, so just be aware of that.
Also, (and this was not a real issue for us) the apartment is directly beneath the flight path for approaching planes landing at Lisbon airport. Our kids actually got a kick out of it because the planes flew pretty low, but it was noticeably loud, even at night.
Otherwise, a great stay and nice location from which to visit Lisbon.