It was an amazing stay and Gabriella is a really nice person. Though she doesn't speak English, she made her best to communicate with me nonetheless, and I had no problems with it. She showed me the nearest supermarket and gave some good advice about what to see in Rome. And she made me coffee every morning!
The location is really convenient. There is a direct train from Fiumicino airport, and the house is in about 5-10 minutes walk from its station. Moreover, there is a metro line in about the same distance, that goes directly to Termini and Colosseo. If you want, you can get to Colosseo by foot in about 1-1.5 hours, but there is almost nothing interesting to see on the way, so there's no use to do that. It aso took me no longer than 20 minutes on metro to get to the Vatican City.
The apartment itself is clean and spacious. All the necessary features are present: fast WiFi, fridge, stove, TV and coffee cooking pot. The only thing I missed was a teapot.
I surely recommend this apartment to stay in.