We loved exploring Testaccio from this apartment: walking through the local garden each morning for our cafe and cornetto at a local bar, and hearing the piazza buzzing with children playing and adults conversing at the end of the day was wonderful. There are not many tourists present, so you are not hassled by beggars or vendors. It is an easy walk to Parco Sevello - Giardino degli Aranci and the wonderful view over Rome, and also Bocca della Verità and Circo Massimo.
The light coming in the apartment is glorious. There is traffic noise from the street below, to be expected as you are in the city, but the double glazed windows work very well in muting this noise. The bed is very comfortable. We had some issues with the internet being inconsistent, turning the modem off and on only improved the signal sometimes, and we ended up using data from our phones.