The apartment is beautiful with high ceilings and plenty of windows. The two main bedrooms are lovely and have views out over the street below. It is a busy street in the evening with foot traffic and restaurants, so it isn't completely quiet but there is very little vehicle traffic and overall the noise wasn't too problematic. The third bedroom is much smaller. The single bed is comfortable and plenty long, but it is the height of a toddler bed (I mean this literally, not pejoratively), so it is not ideal for anyone who has mobility issues.
One of the primary things that drew me to this apartment was the terrace, but it was a bit disappointing as it is in the middle of the building's courtyard so you are surrounded by apartments. I was traveling with my parents and brother and sister-in-law - we wanted to have a glass of wine on the terrace after dinner as a night cap, but we had to start eating dinner a bit earlier in order not to disturb the neighbors by being outside.
Communication with the host was good, she was proactive in reaching out and getting us the information we needed. Our only issue was around check-in as the timing got screwed up due to a delayed train. We had some difficulty in the re-coordination of the check-in time and ended up waiting outside the building for awhile. Not the end of the world, and everything else went smoothly.
The location is really great - only a few blocks from Piazza Navona and with lots of shops and restaurants even closer by. We really couldn't have been happier with the neighborhood and the convenience to all the places we wanted to go. We never needed to use transit once, other than for arrival and departure.
Overall I think it's a great apartment, the issues we had were mostly about how we wanted to use the terrace and the fact that we had one more adult than is really ideal for the space.