The apartment itself is very nice and just as it looks in the photos, small but cleverly laid out. The bathroom is tiny but clean and usable. The area seemed quiet and safe, easy to walk to most of the main sites of the city. The compromise is that it's an old building and up 3 flights of rickety stairs (no lift), without air-conditioning which we knew when booking but didn't anticipate it being quite so hot (over 40C) when we were there! We managed with the fan provided.
Top tip - ask whoever checks you in to make sure the keys work as they are particularly fiddly, especially the front door which we relied on being left open or tailgating neighbours. Our plea to the apartment manager for assistance with it unfortunately went unanswered. Overall we were happy with the accommodation and loved Lisbon, only wishing that it had been a bit cooler so we could have enjoyed more of it!