Teresa's and José's apartment was perfect. It's right at the center with all major sights, restaurants, bars, public transport etc. within walking distance. They were easy to communicate with and our late check-in was no problem.
The apartment is tiny yet it provides everything you need. It was very clean with modern interior and a comfortable bed. However, if you plan to stay longer be aware that the space and facilities (for cooking and the bathroom) are fairly limited. But to enjoy a couple of days in Lisbon it's perfect.