Firstly, all previous negative comments about street noise are now out of date! The apartment was freshly fitted with heavy, double-glazed windows which did a great job of blocking out noise. Most of the time though I preferred the ventilation and enjoyed the sounds of activity from the area.
And the area is amazing! I walked to everything. The train station is perhaps a little far carrying bags, but still faster and more comfortable than catching the bus. Vatican City is no problem. Pantheon, river, fountains, Spanish steps are all close by.
The apartment itself is spacious and comfortable. Plenty of food options in the area, and Johnny's Off-license next door and Open Baladin around the corner had some world-class beer options.
Hosts are great -- speedy and helpful replies.
Overall, highly recommended!