We really liked Valentina's place. Stylish and comfortable. It's close to the train station from which you can go to and from the airport. It's also close to the metro and bus stations. 24 hours supermarket is just 3 minutes away. 40 minutes walk to Colosseum, so it's not in the center of Rome but you can definitely walk there.
Valentina is very helpful and nice. She explained us everything, gave us some good tips.
We had some minor issues with hot water but everything else was superb.
I would recommend staying here!