Sónia's place is a great place to stay when you want to visit Lisbon as a couple - or two friends who don't mind sharing a bed. The location is excellent, not right in the center (so not too much noise) but really close by. Also the neighborhood in which the apartment is situated is really nice, and there are a couple of nice places to eat and drink something, at all hours of the day.
I would definitely recommend staying here!