The apartment itself corresponds well to the pictures. It is a well designed, comfortable, livable, and cozy apartment. It has natural light, nice views, it is not too noisy, and it is in the center of Lisbon. The check-in is easy and the host is responsive.
The only two concerns I have about the apartment itself is that (1) there is nothing to cook with (i.e., no pans, frying pans, pots, etc) and that (2) almost all the TV channels are in German (except a couple in French).
As to the location, it might be a bit deceiving. Although it is only a few minutes away from Praca da Figueira and Rossio, the last 200 meters before arriving at the apartment, which are on a hill, require walking in an area which is in a quite poor state: it is dirty (garbage in the street), does not smell very well (urine and worse), is used for people to do drugs (I saw it in several occasions), and a good number of its buildings are in decay. Although the host reassured me I should not worry, all this can nevertheless make someone—specially someone traveling alone—be worried. It made me doubt about going out at night.