The apartment is very spacious and nice. We felt very comfortable. It is big enough to host four adults (two mothers and two daughters) without being in each other's way. You can easily walk to the Vatican, St. Peters as well as to the city center, and it's also close to the metro station.
We would recommend the apartment without hesistation - just one tip for people who are used to having a proper heating system: pack a warm pullover as it is a little cooler in the apartment during winter time.