Best is the location as it has been already said by previous guests. It is around the corner of Campo di Fiori and close to Trastevere. Of course this means it is in a very touristic area. The appartment is a bit dark with ony one window and the door to the terrace. The terrace itself is surrounded by the walls of the neighbouring houses. When we have been there in Octobre no sunlight hit the ground. When you are in rome for a short trip you won't be in the appartment during the day anyway probably so that is ok. In summer it might be a plus since the heat is less.
The staff was helpful and we could enter the appartment very early when we arrived by night train in the morning.