This is a fantastic apartment. It's spotlessly clean, stylish and modern. (It also has a lift!). The location is excellent. The street is quiet and the area is very charming with some interesting bars and restaurants (and great views). It's easy walking distance to the more touristy areas like Bairro Alto and Chaido. Be warned, there are steep hills - but that's Lisbon!
Mafalda and Madalena were extremely helpful. We had to be fairly proactive in communicating with them prior to our visit, but all information was provided and Madalena was incredibly patient with our late arrival due to taxi issues.
It's worth noting that the apartment street name is very similar to another street in Lisbon 20 minutes away. Despite showing the driver the correct address, the airport taxi took us to the wrong street - and we had the same issue with several other taxi drivers. If you are using city cabs (the only taxis allowed to drive up the private street directly to the apartment) make sure you show the driver the map not just the address.
We had a wonderful Lisbon stay thanks to Mafalada and Madalena. We would definitely stay here again.