We stayed in Sarah & Pedro's flat for 2 weeks: despite being on the smallish side, we found it to be very comfortable. We particularly appreciated the raised breakfast area (at least, we used to have breakfast) overlooking the street. We also *really* appreciated the excellent heating system -- crucial given the chilliness of Lisbon in late November. We were received by Sarah & Pedro's neighbour, Maria, who was very welcoming and friendly. Communication with the hosts was also super easy and efficient.
Moreover, the flat itself is well located in terms of transport. It is a short taxi ride from the airport, plus there are buses passing right outside the building. There's also a supermarket about 15 minutes walk away which is handy.
The flat was spotless when we arrived, and a cleaning service was offered at the end of our first week. The kitchen was fully equipped -- also crucial for us as we tended to have our dinners in.
Wifi worked perfectly, there's a large television... Overall, great!