I really enjoyed staying at Joao & Carla's apartment.
The location (in the heart of the Alfama) was great, really typical and enjoyable. We could easily walk to the town center (approx 15 minutes) or the closest subway station (Santa Apolonia - approx 10 minutes).
The neighborhood was great and the person who welcomed us gave us good adresses to eat, or good places to see.
Last but not least, the apartement is clean, sunny and nicely decorated, which gives a cosy feeling and a sentiment of comfort.
A simple warning: it was a quiet neighborhood so we weren't bothered but you could sometimes hear the noises from outside. So, if you're a light sleeper, don't forget the ear plugs ;)