GREAT LOCATION!!! I don't think you can find many other options with a better location than this one in Lisbon. The apartment was clean, everything was walking distance, and the hosts even accommodated our early check in request.
However, I would like to point out couple of things: 1) the only shower at the Airbnb is extremely small and was not comfortable for us to use (by this i mean we couldn't even turn around in the shower due to the lack of space), 2) we (a group of 6) ran out of toilet paper and could not get a hold off the hosts to get more during our stay. It would have been ideal if more have been stored at the apartment for us to use as back up, 3) the apartment we stayed at was on the fourth floor and requires you to go up several steep and narrow cases of stairs (maybe a common thing in Europe though). This was not a problem for us since we are all in our early 30s but may be challenging for a group with older folks.