Piero was fantastic: responsive and incredibly helpful with our last-minute getaway. He pre-arranged our car for us on arrival and met us at the flat even though we arrived almost an hour early. He is a kind and thoughtful person. He even took the time to provide a Christmas tree for us. The perfect host!
His apartment is exactly as described and pictured - but, as mentioned in other comments, even larger than it appears. It is even stocked with maps of the city and guidebooks in various languages. He provides clear written instructions (again, in various languages) posted for the various appliances, the trash pick up, the heating and a/c.
The flat is a few minutes walk from the tram line to Piazza Venezio, and we walked almost everywhere. Trastavere and is filled with great locals' bars and restaurants and Piero is the perfect host, providing spot-on recommendations we used every day.

All in all the flat was perfect for our family of four and we would love to stay in it again. Highly recommended.