We had a fantastic experience with Inn Possible. Carmo is an excellent host and had everything ready for us when we got there. She also allowed us to check in in the morning as the apartment was available. Unfortunately in our way to Lisbon, we lost our bags and she even received the bag when it was delivered by the airline.
The apartment is in an excellent location and on top of one of the best Fado houses in Lisbon. It is also right by the Lisbon Cathedral, 2 mins away from the tram 28 station and 8 mins from the metro station. We were able to walk around everywhere and found the apartment to be extremely convenient. One thing to remember - the apartment is located on the fifth floor, so be prepared for it :)