Marcello was a great with helping us check-in giving us directions and being available when we needed him. The apartment is very comfortable and spacious in a quiet residential area just outside of Trastevere. There's no metro close by but there's a bus (no. 75) from just outside the apartment that goes to the Coloseum and Termini station from where you can take the metro.
Me and my wife enjoyed our stay in Marcello's apartment.
Must also mention Marcello had a great collection of books. Wish I had more time to read though.
Maybe next time!