My colleague and I spent 3 nights in the Frederico's apartment during a business trip. The owners were very kind and punctual, all of our requests were satisfied. The apartment was clean, spacious and very well situated - there were stations of two metro lines and supermarkets near by. It's only 15 minutes from the airport by car. Just bear in mind that during the colder months you will probably need warmer clothes for your stay - it's an old building and there is no central heating in it. But electrical and gas heaters are provided in the apartment. If I have a chance to visit Lisbon again, I'll certainly try staying at the same place.