We had a really great vacation at Costanza's place.
The location blew us away. Every restaurant and shop we planned to visit turned out to be a few minutes (walking) from the apartment. It's also 5 minutes from the Colosseum and a bit more to Trevi fountain. Everything else there is to see in Rome is up to 20 minutes away.
The place is clean and beautiful and everything is in order and works perfectly.
Costanza knows everything there is to know about the city and is happy to help (she also arranged a great taxi service for us from and to the airport).
The only thing you should be aware of is that it is on the 3rd floor with no lift, so if you are disabled - this is a limitation. But if you're not - it's worth every step.
Don't think twice - it's THE place to be when visiting Rome.