This flat has an excellent location---we walked everywhere, even to the Baths of Caracalla. In spite of its proximity to Campo de Fiori it is very quiet---even though it is at ground level, we heard no noise from passers-by or from traffic. Other reviews have correctly noted that the space is small, but it was enough space for us. The bed is very comfortable.
Because of the ground floor (US first floor) location, we kept the windows shut and the curtains drawn, which made the place feel rather closed. However, running the AC (there are two units, both quite powerful relative to the small space) gave us air circulation. All in all it was a nice stay.