We had a terrific two-night stay in Giovanna's place, which is in the cool San Lorenzo neighbourhood. Giovanna communicated really well and met us on the day we checked in, and the apartment was a nice little retreat from the hot Roman sun. It's safe and secure, had a kitchen with everything you need to cook a meal or eat breakfast, and the bathroom has just been renovated with a great shower. You need to climb a ladder to get to the bed in the loft, but that's clear from the listing. The reverse cycle cooling also works really well.
The apartment is about a 20 minute walk from Termini and maybe an hour from the Colosseum, but it's an easy bus ride to anywhere in Rome. We were happy to stay in San Lorenzo in the evenings though, it's got a cool, gritty, student / artist feel, and we would recommend for local bars and restaurants: Osteria a Piedi Pari; and Bar dei Brutti.