A friend and I shared David's flat for a long weekend in Lisbon. We both loved the city and the whole experience, including our time relaxing at the flat. As there were only two of us, we didn't even use the third bedroom, which seemed nice.
As others have mentioned, it's Lisbon, so there's lots of stairs to climb. It's worth it though, for the views you get from the flat, which are amazing. The sea breeze was also great when we'd come home after a long day of sightseeing.
The area is perfect, very near some busy streets with lots of nightlife but removed enough so as to be quiet at night. Definitely recommend visiting Lisbon, and certainly recommend David's flat.