When you arrive at the house the view is spectacular in all directions. The house is literally next door to a beautiful 19th century Palace (the Quinta de Regaleira).
The house itself is very spacious (two rooms with double beds, another room with 2 bunk beds, a big living room, a well equipped kitchen).
Carlos met us personally when we arrived to show us the place and gave us a local cake which was a very nice touch (and delicious).
There is lots of room for children to play in the garden and on the balcony on top of the house and despite it being August the weather was nice and cool (chilly at night in fact).
There are two issues with the house. The first is Sintra itself. Traffic in Sintra can be pretty bad and you can get stuck for 40m in traffic just to get out. During the day (8-19) the way out is one way and even without traffic it is min a 15m drive anywhere. If you like hiking and just want to visit Sintra this is not a problem, but as a base for other trips might be a little annoying.
Second issue is the amount of dust and the smell of mold in the house. When we told Madalena about it she was extremely nice and helpful, she answered immediately and made sure to bring a dehumidifier into the house which helped a lot, but obviously did not solve the problem completely.