This was probably my best AirBnB experience so far - both for the apartment itself, and for my interactions with Alessandra while arranging it.
First of all, the apartment is extremely well-located on a quieter street about two minutes from Ottaviano metro. This is very close to the Vatican (seven or eight minutes walk from St Peter's or the Vatican museums), but it's also easy to get downtown; the train to Termini means it's also easy to get to and from the airport. There are plenty of decent restaurants in the area, as well as great shopping on Cola da Rienzo; the livelier nightlife is a bit south in Trastevere, but it's easy to get to. The apartment looks on to an inner courtyard, so you won't be bothered by street noise.
The space itself is absolutely lovely. It was sparkling clean, and everything was in good condition: there were some solid characterful old pieces (e.g. a closet) mixed with good new stuff. The bathroom was all modern and well-kept. The apartment was spacious and comfortable, and just the right temperature: I didn't need to use either a/c or heating.
All the appliances you'd need are there: there's a good selection of kitchenware (including coffee pots and electric kettle), dishwasher, fridge, iron, washing machine/dryer, tv, first aid kit, and hairdryer. There's even a safe for your valuables (but be sure to read the instructions before closing it!). Moreover, Alessandra went above and beyond with a lot of thoughtful little touches, providing oil, vinegar, tea, coffee, and a tray of snacks to welcome me to the apartment.
That last touch was typical of the host: she was always very communicative throughout my stay. She responded extremely quickly to messages, and was always helpful: she allowed me to check in early, and when I accidentally locked some things in the safe (because I hadn't read the instructions...) she arranged for it to be unlocked very quickly. The check-in was done by Suzy, who is the wife of the building superintendent, so she's usually around in case of emergency as well: she was always very helpful and friendly.
Overall, I was absolutely delighted with my stay here. I recommend it 100%: I will definitely be back the next time I'm in Rome!