I spent 8 nights at Sharon's place. Things that were important to me: the mattress was plenty comfortable. It was some type of memory foam, which works well for me.
The location was fantastic. Very easy to get to from FCO airport. I took a train and then a six minute walk from the station to Sharon's. Very convenient. I have not stayed in Trastavere before, but found it to be wonderful. It is full of great restaurants. Everything you need is within walking distance.
The apartment is six floors off the ground, so noise is not too bad. Of course, you are in the city, so you hear city noise, but nothing unusual.
Sharon speaks English fluently, which was a plus for me. She is extremely responsive, which put me at ease, because I'm always nervous about finding my way from the airport in a strange city/country. But she was really good at sending directions.
I also found her to be very accommodating. She has some type of water fountain in the hall, which made a noise that bothered me. When I told her, she turned it off. I thought that was really considerate, and I appreciate it very much.
The apartment is also very clean and the area is safe, so if you are a single woman, I would not hesitate to stay here.
It is a small apartment and you do feel like you have a roommate, but I enjoyed having another human being there. Overall, my stay was wonderful, and I would not hesitate to stay here again.