We stayed in the apartment for 3 nights with a 1 year old daughter. We were warm welcomed and were given some valuable recommendations about the cafes/restaurants/shops around. The location is great to explore Rome by foot.
The apartment itself was quite clean and looked as in photos (if there is no sun, it might be a bit darker). It is ok for a couple or for a short stay with one child. Keep in mind the price you pay, so do not expect to get a spacious apartment with a big kitchen in Rome center. A stroller can be left downstairs. Bringing it up is possible, but difficult. There are stairs in the street to reach the apartment "from Vatican side" (so it is difficult with a stroller), however walking another 100m solves this problem.
There was no washing machine (as was indicated), however I found a hair dryer and an iron (which were not indicated) and was happy about it. We also used some coffee and tea.
A soundproofing is not the strong point and can be improved.
Another hint: take slippers, as the stone floor might be cold.