The location is absolutely perfect. We walked to Piazza Navona multiple times during our stay. We also walked to Trevi Fountain and Campo de Fiori market.
The apartment itself is very pretty and cosy. IMO, it would be better for 3 people rather than 4, and an absolutely ideal place for 2. The sofa-cum-bed in the living room can get a little tight for 2 people.
The place was very clean and everything was well provided.
Even though there is an elevator in the apartment complex, the elevator doesn't go to the first storey. Therefore, if you have someone who has trouble climbing stairs then this would not work.
The eating recommendations from Roberta were very good. We tried out a few of the restaurants on the list. The eating place right below the apartment was fantastic.