Spent five nights here as part of our honeymoon. The apartment is on the second floor of a building right in the heart of Trastevere just around the corner from the main piazza so it's central to everything, but we had no issues whatsoever with noise. As it's on a corner there's also plenty of natural light.
Spotlessly clean and very well equipped, even Netflix (which came in handy on the one evening we had an absolute biblical thunderstorm and downpour!)
Host was quick to reply to any queries we had and provided excellent info on arrival on places to eat etc., also on the less glamorous things like where the gas tap & water stopcock were. The bottle of limoncello provided was lovely too!
All the main sights within walking distance, taxi rank and supermarket both about 5 minutes walk away.
Wouldn't hesitate to stay here again the next time we return to Rome.