I spent 5 nights in Rui & Elsa's flat. Communication was great and check-in and check-out went smoothly. The flat is well-equipped and situated in a quiet street walking distance to most of the sights (keep in mind though that this city is built on hills :)), lot of restaurants, metro and tram lines and a train station. I'd definitely recommend it for solo travellers and couples as a base for there exploration of this great city.