Had a great stay at the Festina Lente. The flat is located literally around the corner from the metro station (Ottaviano). It is on the raised ground floor with heigh ceilings and big double glazed windows. The rooms are large and well proportioned with all amenities you could want. There are shops and restaurants literally on your doorstep and the Vatican is 10 minutes away on foot.
Luciana and her family made me feel very welcome on arrival and even had an Easter cake for us to enjoy during our stay (which was delicious!). I would definitely recommend this flat for anyone looking for comfortable stay in Rome.
The only "negative" is that as the flat is just above street level, it might get noisy if you want to sleep with the windows open, but there is air conditioning otherwise.