We spent 4 fantastic days in the flat. It's a tiny studio but it's enough for 2 people. It was brand new when we stayed there. It's very nicely decorated. Even though it is on the ground floor, the street is pretty quiet and except for the bedroom, the flat is not dark. And there are so many options around for eating out that we spent a lot of time outside.
The flat is located very centrally. You can basically walk to the main touristic areas. We really liked Principe Real and Barrio Alto which are 10 mn walking distance of the flat. Rossio train station is also pretty close (15 mn walk) - you can take a train there to Sintra.
Vitor was extremely helpful when he welcomed us. He gave us many tips on things to see in 3 or 4 days, places to eat, booking a taxi to the airport etc. In the flat there was also a nice welcoming pack with coffee, tea etc. He made sure he stayed in contact during our stay and that everything was going well! I would definitely recommend staying in the flat.
The wi-fi was slow at some point but it worked.