What a great apartment! I stayed here with my sister and four kids, ages 7-16. We LOVED the rooftop terrace. Fantastic view. Sitting there every night watching the light fade behind St. Peter's, listening to the church bells and the birds … wonderful!
Trastevere is VERY lively at night and yet the street itself is quiet. Plus being on the top floor of a 5-story building helps reduce noise. ;) We felt very safe there.
Chiara and Maria were great and very responsive to concerns. We had a recurring problem with the electricity and Maria came within hours with a technician who fixed the issue. And as long as the electricity is on, the wifi works great - very reliable.
A couple caveats - be aware that all old buildings have their quirks! There are 70 steps up to the apartment, two tight spiral staircases inside the apartment, and the windowsills are fairly low (and it's a long way down). So it's not great for small children or anyone with mobility problems. Plus the lack of a/c makes it pretty hot in June. The rules for separating garbage/recycling and taking the bags to the right place at the right time is a bit of a nuisance, but walking to Piazza Trilussa with my bags made me feel a little bit like a local.