One of the best experiences I could've imagined. Marco's place is located literally 5-20 minutes away from any sights by feet, and the neighbourhood (part of Trastevere that is closer to city center) is just wonderful.
Apartments itself is very, very sweet. A lot of space, it's stylish, but with simple decorations and furniture, beds with cool blankets and pillows, and kitchen has everything you need.
I do recommend this place a lot.