We can really recommend Home Sweet Sun. We stayed here for three nights (and 4 days) and we had an amazing time. The apartment looks exactly as described by Alessandro and Mariasole.
The interior is very beautiful and there are many facilities in the apartment: bathroom, blowdryer, airco, television, free wifi
etc. The location is also superb. There are small shops and restaurants in the street where you can buy lunch or some colds drinks. The metrostation is really nearby (5 minute walk) and the Vatican is also nearby (10 to 20 minute walk). Alessandro and Mariasole are very nice and helpful hosts. At our arrival we received a map of Rome and instructions to get to the city centre. On the day we left, we could leave our luggage after the check-out time in the apartment so we didn't had to carry our luggage the whole day. Alessandro also printed the direction from the apartment to the airport (Fiumiciuno). On our birthday they gave us a present, which was really nice. If you're looking for a great apartement and location in Rome, you should definitely go to Home Sweet Sun!