Mario is a good host. He personally made my stay better talking to me all the time I was in the apartment (we exchanged a lot of views about many topics). His place is well positioned close to Copacabana beach and not far from Ipanema, it is clean and secure (the room has its own lock and key, as well as an electronic safe).
Unfortunately, a problem made me come back to my city three days after arriving at Rio, but I would recommend staying with Mario while in Rio without hesitation.