I very much recommend this lovely apartment! I found it in pristine condition and immaculately clean. The kitchen, even if small, was very well equipped. The bed mattress was excellent, firm and comfortable. The bathroom was perfect. The best thing was the light: the huge windows allowed the winter sun to enter fully inside. The lovely balcony, perched surprisingly high, has an impregnable and beautiful view over Lisbon. I found the location great: in a quiet traditional residential neighbourhood, within walking distance of multiple metro lines, with multiple little shops nearby.
Its only drawback, as others have mentioned, is that it is right in the pathway of planes landing into the airport. I was there in the winter, and with the windows closed this was certainly not a problem.