Can highly recommend Nuno's apartment. It's in a good location to explore the city, with public transport nearby and downtown is walkable. Nuno is extremely friendly and was contactable at all times.
One minor complaint - the only bathroom in the apartment is in the bedroom and the door doesn't really shut properly (this may have since been fixed). Not an issue if you are a couple but not ideal otherwise.
However, I can highly recommend this place to anyone looking to stay in Lisbon - it's a great spot.