We stayed for 3 nights in the apartment of Massimo.
Unfortunately we did not get the chance to meet Massimo, but everything went fine, we could reach him very easily for questions. We received the keys from his cleaning lady, who was really helpful although she could not speak really good English.
We had to share the apartment with other people, but we did not see any of them so we were not bothered by anything. Our room was very clean and quiet. The apartment is in a very nice area, 5-10 minutes walking from a Metro station (which are very convenient in Rome).
We can certainly recommend the apartment of Massimo.