I found Bárbara & Nuno very welcoming and their communication (in English) was clear and helpful both before and during our stay.
The apartment is very clean and modern with kitchen cupboards had everything we needed during our stay and were nice touches with cookies and coffee pods for the coffee machine and a lego set for the little one. The beds are supportive and comfortable and quilts were snug and warm. The small lift takes you up to the apartment, which is great for weary traveler sight-seeing legs!
Location-wise it is very near to a metro station for central and a train station - handy for taking a trip to Sintra. Also there's a mini-supermarket literally a few doors away, a bakers a couple of minutes walk. There's a few local bars and a pizza restaurant nearby. Campo Pequeno - a multi-function center including an underground shopping center with supermarket and food court 5-10 minutes walk away. There's a theatre and cinema there, but we didn't visit that. There's a taxi rank within 5 minutes walk. It cost 10.45 euros for our family of 3 to return to the airport with 2 bags of luggage. There's a car-hire shop we found next to the nearby train station, which came in handy to visit more remote parts of Sintra.
Lisbon's airport is in the city and we could see the planes in the distance whilst having breakfast and dinner in the dining area. This was of great amusement for our little one. The noise is noticeable but not loud enough to bother us - in any case we noticed no planes in the night or early morning.
Living in the the UK we are used to central heating, though given Lisbon's mild Winters and hot Summers, I suspect people generally do not have central heating, so we found the flat a touch cool at first during our March visit - probably a bonus for the hot Summers. However, there are heaters/air-con in the bedrooms and in the living room and bathroom, which were very useful.
Overall, we enjoyed and were happy with our stay here!