Enjoyed our short stay in this apartment. Marco was great! Answered all my questions, had someone there when we arrived, called me when we touched down to make sure everything was good, allowed us to leave our luggage the day we checked out and come back for it later... His help really made it easy and stress free. My thanks to him!
As for the apartment itself (We stayed in Unit 3), it's fairly basic, not a huge amount of charm, but clean and functional. We were there in winter and the heat worked fine, plenty of hot water, towels, etc... A decent amount of space. A place to sit and eat. Didn't really use the kitchen, but it seemed very workable. One bed is a sort of futon-ish rollout in the living room and then there is a proper bedroom. Bathroom is through the bedroom. We were there with two teenagers and it all worked out nicely for us. Price was great and we really did like the neighborhood. Some great little trattorias nearby and easy walking to everything (Da Fracesco was really good - Piazza del Fico, 29). Grabbed a bus to go to the Colosseum, and that was easy (#87 from near Piazza Navona).
One note, lots of fairly steep stairs to get up to the apartment. Was not an issue for us, but if stairs are difficult for you, this might not be a great choice.