As good as one can expect with the reviews--I was satisfied and happy with everything. Fabrizio was punctual, flexible and communicative. The flat was as-advertised (quite nice, fairly quiet). Convenient location near a local market and a 24-hour Carrefour, a 24-hour bar, a good pizza place, as well as a nearby bus stop, and a metro about 10 minutes away. It's actually a pleasant 40 minute walk to the Forum/Colosseum, if you're feeling like the scenic route. WiFi was fine. Comfy bed. Air conditioner a bit loud but works very quickly (probably a connection between that), and windows alone were usually sufficient anyway. Don't need to climb up any stairs or use the elevator to get to the flat, which is a welcome relief after walking all day.
Overall, perfectly satisfied with the stay and Fabrizio's hospitality.