We stayed here for 12 weeks.
The neighborhood was great - lots of good local restaurants, bars, pastry shops etc. The place has great proximity to all the public transit, but also very walkable to many of the major sites. About 20 minutes to the Coloseo, or 30 minutes to Teatro Marcelo.
Nadia and Filippo were excellent - very responsive, greeted us at checkin and texted very quickly if we had a question. They even helped get us a reservation at Felice (which was disappointing, BTW, try Fraschetta di Mastrogiorgio instead). Also, on the subject of food in Testaccio, Pasticerria Barberini on Marmorata was very good, and we thought the best gelato in the neighborhood was at Panne & Co on Marmorata, although the visciola at Giolitti was a close second.
The terrace off the kitchen was great in the hot weather - a very good place to drink wine. The kitchen is not large, but is serviceable for basic cooking.
Would definitely recommend Nadia’s place.