We with my husband stayed in Cristina's apartment for 5 days during New Year holidays. We chose the apartment because of its close location to Vatican (as it was my husband's desire). However, afterwards we found out that spent most of the time on the other side of the river, as most the attractions are located there. As a great benefit of the apartment, you may find Coop supermarket and huge open market just few meters away from the house. Bus stops are also conveniently located nearby.
Cristina herself greeted us and was extremely kind to wait for us late in the evening as we had the late flight. She warmly welcomed us (even with bottle of vine) and spend her time telling us useful tips about transport, museums and restaurants. She has prepared tourist kit with all addresses, maps, names, etc, we found it very useful.
The apartment itself is pretty small, so we found it not very comfortable for two people at the end of our stay, it is very frequently used by the tourists, so despite everything was clean (bed, towels), we had the feeling of overall untidiness. Partly it was because of the bad smell that came from the bathroom. I saw the same comments about the smell in previous feedbacks, so understood that it is a regular problem. We tried to keep the bathroom closed all the time, but should you once forget about this rule and you will have the smell all around the room. You should also keep in mind that sound isolation is not very solid, as we could hear the conversations in another room. However, we were lucky with the neighbors and had comfortable sleep.
And also don't forget warm socks if you are visiting Rome during the winter time, as cold floor (which is a huge benefit during hottest Rome summers) may come as an unpleasant surprise in winter.