The flat in Lisbon had everything one would need for a great stay. It was super close to public transit, making anywhere in the city easily accessible. It's only a 30 minute train ride from the airport, and then a short (uphill walk) to the apartment from the metro station. We had no troubles checking in. The place was nice and very clean (newly renovated), and we had great contact with the host Daniel and Liam on WhatsApp.
During our stay we met a lot of the neighbors, and they were all very friendly and nice. Be sure to check out the park / dog park (Graca) nearby. Such as nice place, with a small cafe as well. The area is really nice, and the people are friendly. We felt safe the whole time staying there. Please note that while the apartment don't have a balcony, it makes up for it with a big bathtub and nice surroundings. The hosts Daniel and Liam was very responsive and very helpful during our stay, and they even let us keep our luggage in the apartment after check-out, since we had a late flight and they didn't have guest checking in before we left. We really appreciated that as well.
All in all, a great stay, and a great classic Lisbon location. Would go again.