We had a great time exploring Lisbon from the apartment, with Nuno as a wonderful host, always available and helpful. He picked us up at the station (and would have come to the airport), showed us around a bit and gave useful tips for the city. The neighborhood is very calm and feels remote at night, while buses, trams and the Metro are just about 5 minutes away.
Just be careful when you turn on the hot water at first, or it might boil you alive...;)