I can't imagine a better host or a better place to stay in Lisbon.
Diogo is both extraordinarily helpful and informative. He helped us with the luggage when the cab dropped us off, he had a bottle of wine and a bowl of fruit waiting for us and, after explaining the apartment to us, was gracious with his time in suggesting different things we might do in the city. He had maps and brochures available as well. During our stay we communicated through What's App and Diogo was always available to answer questions. On our last day, he ordered a cab for us and had his cousin come over to help us with our luggage.
The apartment itself is terrific. As much as we like to eat out, we also like to cook and the kitchen had everything one could want for cooking. We needed to wash some clothes and the washing machine works well and the small patio has lines available for drying clothes. Every room in the apartment is tastefully decorated. It's obvious that a good deal of thought has been put in to the design and furnishing of the space.
The location is also great. While the actual street isn't much to write home about, it is wonderfully located for walking and visiting the city. Rossio, restaurants and shops are all nearby.
You can't go wrong here.