I can highly recommend booking Trancesca's apartment.
Not only is the apartment well equipped with everything you need (kitchen supplies, etc) but is is also nice and very well located (very closed to the vatican state).
On top of that, Francesca is a very nice and helpful person. She adopted to the time we arrived and left with regards to receiving and handling over the keys. More over, she was very nice in explaining us the best way to get to the apartment and helped us with every question we had with regards to getting around in Rome, to find restaurants, supermarkets etc.