We stayed at Tiago's apartment for 3 days in January, a company of 3 adults and 4-years old boy.
Although Tiago wasn't there, he replied almost immediately and was very helpful. The apartment is quite small for 4 persons, but for the short stay it should be OK. We were slightly disappointed with a very small kitchen, but taking in mind the price (it's unbeatable!) and perfect location, I gave it 5 stars. It was very nice to arrive to this literally warm place (the heater was turned on in advance) and find a CD player with good music to hear (my son likes Frank Sinatra :)
If you want to explore Sintra and its surroundings, the bus stop from which all routes to the castles and parks start is 1 minute walk from the apartment, the famous Sintra train is 10 minutes away.
We had a good time there, thanks Tiago!