My girlfriend and I stayed at Marco's apartment for 5 nights and it was great. In a quiet side-street but with lovely restaurants right outside and cafes, bars and shops all within a couple of minutes walk.
We didn't use the sofa bed, so the flat was a decent space for just the two of us - it is fairly small but had everything we wanted, and we spent most of our days and evenings exploring the historic city. For this, the apartment is ideally located.
Pantheon is 2 mins leisurely stroll away, Piazza Navona 3 mins, Trevi under 10 mins, Vatican about 25 mins.
Marco helped us with directions and advice for arrival and then sent me a list of nice cafes and restaurants which was well appreciated.
We arrived and left on late-night flights - Marco was very accommodating with late check-in and check-out times and was helpful with any queries.
We loved our stay in this apartment and would definitely try to stay here again if we return in the future.