I stayed only for one night on the eve of my flight. Sara answered many of my questions about transportation before my arrival. She also made tea for me, quite a welcoming gesture on a rainy day.
The room is very cozy, and clean, and looks recently renovated. The internet is very fast. There is very faint cigarette smell but it didn't really bother me. It would've been different if the smell was stronger.
Sara's place is very close to the airport. The 101 bus is only 5 minutes walk away, and stops at both terminals 1 and 2. Once you get on the bus, it's only 10-15 minute ride to the airport. Budget more time if you need to take T4 free transfer bus, conveniently boarding from where you get off 101 bus. Make sure you have at least a metrobus ticket for 101.
The metro station is even closer, only a couple of minutes away. You can easily take the metro to downtown Madrid. But the line does not take you directly to the airport. Use the bus instead.