Location!!! in the middle of everything and close to the main squares and shopping streets. and that is the most important thing in the apartment.
nice place, clean and organized. the room is a bit small but we understand that comparing to the city its good. the showers are vary small. probably won't be convenient for everyone. things that are important to consider: the apartment has a smell of old and a bit moldy but it's like that in many places in Portugal. the apartment is the first floor with no elevator, wasn't a problem for us. there is a lot of noise from the street and from the building. it is very significant. also, didn't bother us, because we so tired from traveling in lisbon all day :-)
overall, it's a very nice place to stay if you want to feel the city. the check in was comfortable and convenient.