The area is not central, the public transports are a little too far or not convenient, but the price is interesting compared to a similar level of comfort in the real historical center. The neighborhood is quite deserted at night.
We fell like the comments we read and that made us choose the place were quite different from our own perception.
The apppreciation of the neighborhood will depend on your own standards, but as two Parisians ladies in our 40s used to big cities and travelling and even knowing the place was not central, we didn't expect to feel so far away from the center for a classic tourist trip when you need convenient access to the central attractions. This might work better for a longer stay and different purposes. Also, "residential and quiet area" in that case mostly appeared to us like very empty at night (very few restaurants or cafés around) and deserted streets, impossible to reach by metro, so we decided to get back every night with a taxi to feel safer after a late night in the center. Even if it is probably not dangerous, we didn't like the atmosphere, with very little street lighting. This is probably okay when you are here for a while but not when you don't know the neighborhood. We thought being in a less touristy area would be nice to get in a real Roman mode, but we felt we lost a lot of time figuring all this out.
We were greatly welcomed by Rowena, the lovely intendant/housekeeper who is very friendly. The room is nice and newly renovated, but small (it is not one of the apartment described in the other comments) and we appreciated that Rowena managed to offer us separated beds as I asked, the room is usually settled as double room, better for a couple sharing bed.
Be aware there is no window in the room, it is a glass door on the ground floor. The listing mentioning a terrace, we didn't expect a ground floor outdoor space with no real intimacy from the rest of the courtyard, as opening the door was the only way to get fresh air (which you can do in the morning but not at night of course for security reasons.) We couldn't leave the bathroom window opened either for the same reason. There is air conditioning which we didn't plan to use as it was around 15 C at night, but with no window we definitely need it as the room gets hot quickly.
The surroundings of the house are very quiet (almost no cars in the tiny street), but Alessandro and Valentina own a dog who is nice but not well behaved as we heard it in the morning and anytime there was someone passing by in the street. If you plan to wake up really early like 7 you might be fine, and we had a very tight schedule ourselves, but this is not what you expect during a vacation. There was also construction work starting quite early, and if as a owner you can,t help it, we would have appreciated to have a word from Alessandro about it. We met Alessandro once and had a nice and long talk with him, he tried to reassure us about the safety of the area, but we didn't get over our first impression, this is a personal appreciation and it seems that the other guests staying in apartments upstairs got different impressions, so it basically depends on your level of requirements and your own way of life.