This is a really nice, clean and cosy place, in a great location next to several attractions by foot. João Paulo was an awesome host, very friendly and gave us plenty of tips about the place and neighbourhood.
For the sake of a fair review, expect a bit of exercise every time you get in the apartment as it is on the top floor of a building with no lift (as in most old buildings in the area).
Anyway, I'd recommend João Paulo's place and would consider going back if I'm in Lisbon again in the future.