Carlo's place is ideally located - less than 30 minutes walk from the main landmarks such as Vatican, Coliseum, Trevi Fountain and such - in a charming little street and a nice piazza just a few meters away. The place is small but the bedding is great, and Carlo was very much accommodating regarding check-in and check-out.
The only downside was the noise. The appartment is located on the ground floor with just windows and a glass door separating you from the street (curtains are preventing people from seeing you), and the glass is very thin. We could hear everything in the street, from people talking to cars passing - and quite loudly. There is also a bar nearby, which was quite noisy on our first night (sunday) but ok on the second one. On both nights when we came back we had people seated down and having drinks right underneath our windows and had to kindly ask them to leave so we could sleep. Two small issues were also the wifi not working and the water pressure of the shower, which was incredibly low.
That said, the perfect location of the flat was still worth is for us. If you're into nightlife and coming to party or if noise is not a main criteria for you, then this is a very great place.