We had a wonderful time in Lisbon. Though small, the apartment has the perfect size for two people. It was all posh and clean, so we liked it very much. You can reach the castle area and central places like Rossio by foot in only 5 minutes. The initial stop of tram 28 is also only 5 min away. You just should not be afraid of stairs, but when you are, then Lisbon is not your city anyway. ;-)
So all was fine and thanks again to Carlos for the hospitality!