Antonio's place is in a fantastic location, 10 minutes up the hill to Graca, 10 minutes over to Alfama, and 10 minutes down to Rossio.
The apartment is quite compact, but very well designed to make great use out of the space. I worked remotely from there, and felt very safe, comfortable and at home. It was very clean and well equipped, and was also very quiet, which is always a bonus in a busy city - plus there is a nice view of the castle from the window.
Antonio was very responsive and helpful, and was kind enough to be flexible on my check-in and check-out times, which made things much easier. I'd defininitely recommend staying here for your trip to Lisbon!