My colleague and I stayed in Dario's apartment for a week while working in Rome and the place was pretty much perfect. Handily located close to the Metro (Repubblica) and Termini, it was also within walking distance of places like Piazza di Spagna and the Trevi Fountain.
The apartment was clean and well appointed with modern bathrooms and a small kitchenette, not really suitable for the cooking of anything more than simple meals but really there is no need to self-cater as the local restaurants all around are good quality and very affordable. Our particular favourite spot for breakfast was D'Angelo right next door on the corner. Also the elevator is a plus - not always available in Roman apartment buildings.
Dario was an extremely helpful and efficient host who answered any questions promptly and assisted with information and transfers. I wouldn't hesitate to recommend him. Grazie Dario!