Very central location (3-min walk from the Spanish Steps) yet safe , even late at night. Apartment is next to a 24h Carrefour, and there are many decent and reasonably-priced restaurants and breakfast places all within the vicinity. (It is also a 3-min walk from the Spagna metro station, even though we walked everywhere.)
Only thing to note: you'd need to let the host know if you'll like the radiators to be switched on, as they are pre-set on a thermostat. Guido was very responsive about it, so that certainly helped!