Although I only stayed in Mario + Caterina's space, I wished I could've stayed for longer! The building is conveniently located by the tram stop and walking distance from both the Firenze Santa Maria and Firenze Rifredi train stations. I had no trouble finding my way to the apartment. The room is spacious, clean, has amazing light from its cute little balcony, has a comfortable bed, and all the amenities (large desk, outlets, fridge, microwave, etc.) The private bathroom is similarly great.
As for Mario + Caterina, they were very quick to respond to messages before + during the trip, offered flexible check-in despite the fact that I booked two days prior to check-in, and were welcoming when we interacted. They are in a separate part of the apartment, so there's not many points of interaction with them during the stay.