We are a couple and stayed an Antonietta's place in Celio for 6 nights. The apartment was clean and had everything we expected as listed. A/C worked well (very necessary in 90F+ degree heat). There was a minor (few hours, maybe not even an hour) blackout in the neighborhood one day and the hot water heater went out, but we sent a message to Antonietta and she was over quickly to restart it.
If you are more than 2 people and/or staying in Rome for an extended period (more than few days) and brought a lot of clothes, storage might be a little tight. We used the second bedroom to take our clothes out of suitcases and stack on bed as only one closet was available in the other room and hangers on a freestanding rack were a bit scarce. But really not a bother. The apartment has a small washing machine which worked fine.
A/C worked well and wifi was operatonal for our phones although not our tablets. We survived.
Celio is a great location, nice informal restaurants/enotecas nearby to try. Busses/trams to Centro Storico, Piazza di Spagna close, too.
Strangely, no coffee maker or even stovetop espresso pot, but there is a caffeteria right across the street to get your morning capuccino and afternoon espresso.
All in all a very comfortable place and a good convenient stay!