The place is very well maintained, and Madalena and Julia were extremely professional and accommodating. Julia met us when we arrived and made us very comfortable (include giving us a bottle of wine). The place is exactly as advertised: clean, comfortable, simple and effective for a quick trip to Lisbon. Overall, the two of us were extremely happy to stay there for a couple of days.
There were only two things that concerned us about the place: The bathroom is extremely small. This was clearly stated in the description on Airbnb, so this is no fault of the hosts. However, we didn't grasp exactly how small. It's tiny even by the standards of small European flats. I'm a little over 6 feet and had difficulties closing the door behind me and squeezing into the shower.
The other concern is the neighbourhood (Barrio Alto). It's very central and convenient, but it's also pretty loud and full of partying backpackers. At the same time, it made it very easy to find places to eat and drink at all hours. Some people will love this, and others would prefer a quieter neighbourhood. It just depends on your plans for Lisbon.
Despite those two points above, it really was a great stay and the hosts do a fantastic job.