The location is perfect; it is in walking distance to many of the major sights: Piazza Navona, Trevi Fountain, Spanish Steps, Pantheon. We easily took cabs to the Colosseum and the Vatican since we were traveling with my parents, but you can walk there as well. There are great restaurants near the apartment and plenty of hustle and bustle to make you feel the excitement of the city. It does get noisy-- especially at night, but it didn't bother us.
The flat was spacious and restful. It is beautifully decorated with a mix of old and new world style. We were 7 guests-- 4 adults and 3 teenagers, and there was plenty of room for everyone. The AC and wi-fi were great, although one room is not really air-conditioned, but will cool off with the air from upstairs.
Upon check-in, we were instructed to not use more than one shower at a time because of water pressure. That was disappointing, since the 3 full baths were one of the reasons we had selected this space.
One thing to note is that there are A LOT of stairs to get to the apartment. It's an OLD building, so the stairs are worn out and can be difficult to manage-- you need to walk up and down them very carefully to avoid slipping.
Another thing to know is that the "flexible check-in" requires and additional fee to be paid separately. That took me by surprise, but since we were arriving in Rome at 8 AM, we didn't really have a choice.
Overall, we enjoyed our stay. It was a great way to begin our trip to the most beautiful country in the world.