Exceptional.
I stayed in Lisbon during the week for a conference, and since it was my first time in the city (and in Portugal!) I decided to stay over the weekend to explore it. Communicating with Rita (I haven't had the pleasure to meet Miguel) was extremely easy since she is basically most of the time available on whatsapp, and we could agree on my check-in time with a minimum notice. She is exteremely nice and sociable, and always willing to help - when I asked her the best timing to arrange a taxi, she offered to make the reservation for me, to make an example. The apartment is lovely and very well kept, and they have created a custom-made city guide that includes plenty of suggestions based on their experience. The location is also perfect - a few steps from the Avenida de Liberdade, which is a pretty convenient point of reference for going pretty much wherever at least as far as the center is concerned - my orientation sense is pretty lame and yet I have to say that finding my way around in Lisbon and to the apartment (I was always alone when going back home since my friends stayed elsewhere) was surprisingly easy.
While the apartment can accommodate four people sleeping-wise, I would personally suggest it to close friends or family (or solo-travelers like myself or couples, of course) since there is no real separation between rooms and the 'living space' would have to be shared.
Overall, great experience. Would definitely go back!