Great listing! Stylish and very clean. The hosts are very responsive too. And the location is incredible! From the Collosseum to the Vatican, to the Villa Borghese, we visited all tourist attaction without the need of any transportation. Of course, you still have to walk quite a lot, because it is a big city, but at least you start from the very center of the touristic area.
Indeed it is so well located that, if you wake up in the middle of the night, you can take a 5 minutes walk to the Trevi Fountain and enjoy the spot at the only time of the day that it is not completely taken by the crowd of hundreds of tourists, and five minutes later you can go back to sleep!
It is located in a quite busy alley, so you may experience some louder noises. But the isolation is decent when you close the windows and the air conditioning works quite well. And, of course that is a location you will choose if you whant the be in the middle of the party!
Also, the washroom is quite tight. It is very stylish, very well renovated and was super clean, but if you are tall (I am 6'6"/1.96m tall) and/or are overweighted, you might have some discomfort in the bathroom. But that is nothing you can't handle.