Mario's apartment is fantastic for travelers looking for a pleasant space in Rome. We stayed here for 5 nights in December and were very happy with the space, location, and value. The apartment has everything necessary for a short stay and has many great features. There is a lovely balcony that looks out onto a courtyard, a functional kitchen, and a ton of closet space. Although the apartment is a long walk up the stairs (5 flights), it's worth it.
The apartment is a short walk from Termini Station and close to 3 and 19 tram lines, so it is easy to get around the city but can be a little more challenging to get home after the tram shuts down around 10pm.
Mario is a great host and gives very helpful tips about Rome. He responds quickly to questions and wants you to have a great stay. I would highly recommend booking his apartment.