This is such a great place to say in Lisbon. The location is just perfect. For a short or long stay, I think this flat is a great choice, and I will definitely try to stay here again next time I'm in Lisbon.
The flat is very spacious, and it's easy to make yourself feel at home. There are windows on three sides, plus a nice skylight, and the views are fantastic. It's very well appointed and tidy. Maria was really great with her helpful tips prior to my arrival. She saved me from making a huge public transit error!
The nearby shops offer everything you need (time out market just down the hill, a supermarket, produce shop, and butcher right around the corner, plus an amazing cafe for breakfast). The access to public transport is a huge plus, just a five minute walk to the Baixa-Chiado stop, and it's right on the popular #28 trolley line. For the trip to Belem, it's also an easy stroll down the hill to the Cais do Sodre station. For Sintra, the Rossio station is a short walk away.
To me it's basically the ideal place to stay in Lisbon. I really lucked out. Plus you are on a top floor, and the windows are excellent at keeping out any street noise when closed. The skylight near the bed can be left open all night, as the noise from the street does not carry through.
Highly recommended!