Great location in Trastevere, right off the Tiber, within about a half hour walk of most major tourist attractions (Colosseum/Forum, Vatican, etc.). It's also a trendy student area, so there's loads of great restaurants and bars just around the corner. That said, one of them is literally next door, and it seems to close around 2:00AM, so be aware of that if you're a light sleeper.
The apartment itself is really cute and cozy - the bedroom is at basement level (and has AC) so it's quite cool, which I'm sure is especially nice if you're travelling during the hot summer months. The washing machine is also handy, though due to the humidity we couldn't get much to dry in time.
Overall Arianna was a great host - very friendly, helpful, and responsive - and we had a great time!