The apartment has an extremely well-equipped kitchen, is bright and air-conditioned (even in mid-May Rome can be really hot), and has an enormous amount of storage space. The owner is gracious, and the greeter is efficient and friendly. We had a little dishwasher problem, but it was quickly fixed and we received a discount. Because it is a third-floor apartment (fourth, by American floor count), the elevator is a good thing to have for those of us who bring more luggage than they should.
Once you close the double-glazed windows, it is surprisingly quiet -- surprisingly because the Via della Lungaretta is filled with tourists starting around noon. They keep themselves busy until midnight visiting the zillions of shops and restaurants. After a day of Rome, you need peace and quiet because this is a town where sotto voce is not practiced, and this place gives you that peace and quiet. Just being able to open the front door and entering the cool hallway, extricating yourself from the stream of tourists, is a privilege.
The location is superb: about 30 minutes walking from the Colosseo and Foro Romano, 40 minutes from the Vatican, a 5-minute walk to a taxi stand. And, of course, in the heart of Trastevere.