Location, location, location! If you are in Rome to see all the major sites and are planning to do some walking (and why would you want to see Rome any other way!) then this is the place for you! It is within a couple of kilometres of many of the major sites and just 500 meters from Vatican City.
The apartment itself is big and bright with amazing views. We were very comfortable and had just about everything we could want. Our hosts were very helpful, arranging for a driver to pick us up and drop us off, which was most helpful after a long days travel and a very early departure. They also had information on local grocery stores and restaurants. We tried a number of these restaurants and the food was always excellent. They were very quick to reply to any of our questions.
I will note that, because we were close to the Vatican, the street outside the apartment was very busy, but for us it just meant we could watch first hand, Rome's daily life go by.