I stayed at the Pausada de Sant'Ana for 5 weeks and totally enjoyed it: it has just the perfect position to be both in a quiet street but also very close to the centre or to any kind of public transport to reach every corner of the city.
Ana and Luìs are amazing hosts that take really great care of the houase and its guests, I never had any problem of any kind during my stay and they are always very welcoming, positive and available for any request or question: when a guest asked for a bottleopener it appeared the day after and when somebody somehow locked the door of one of the bathrooms they managed to solve the problem quickly and without any unpleasant long wait.
My room was at the top floor: even if the window may seem small, it let a lot of air and light in, the temperature was perfect during the night and a fan was available for the hottest days.
They keep the house (both rooms and common areas) very clean and tidy and there's always somebody answering right back when you try to contact them.
It really felt like home for me and was definitely the best Airbnb experience I ever had so far, if I'll ever get the chance to go back to Lisbon I wouldn't choose any other place to stay: super suggested!