The apartment is small but has everything you need - even a washing machine. It's perfectly located if you travel by train. All the points of interests are in short walking distance. We took the bus just once to get to the Vatican - even this would have been possible in an hour walk though. We felt safe the whole time.
(If you like vegan food, checkout Rifugio Romano (less than 10 minutes walking distance). Best vegan pizza I ever ate and they even made a glutenfree one for me!)