Lucia's place is very nice and well kept. The neighborhood is absolutely wonderful, with great cafes, pasticcerias and restaurants right around the corner. Its relatively quiet at night and we felt safe the entire time. You will need to take a bus or metro to get to all the major sights, but that's probably true regardless of where you stay.
Lucia's place is managed by a third party so you will probably be communicating directly with them instead of Lucia. This worked fine for us, but it would have been helpful to know before we booked. Also, as of our trip, Airbnb does not collect the Rome city tax of €3.50 per person per night, so the host will collect this directly when you arrive. It's not a scam, but you should know this ahead of time. It would be better if Airbnb would collect this through their own billing system, but they aren't at the moment. Be sure to account for this when you book.