Absolutely fantastic location! We walked everywhere from the Forum/Colosseum and Circus Maximus to the Borghese Gardens to the Vatican. Trevi Fountain, Pantheon, you name it - and you can probably walk there. (Granted, we were getting nearly 20K steps in, but it is walkable. The apartment is also very close to a taxi stand.) We loved being right around the corner from the Piazza Navona and incredibly delicious gelato!
Jacapo was a fantastic host, extremely helpful and an excellent communicator. He met us as we arrived from the train station via taxi, and he had good recommendations with a map showing us what things we might want to see/do and how to get there. He also arranged a ride to the airport for us, as Rome was the last city on our trip.
The apartment is pretty large. The layout is a little awkward, particularly the bathroom. There are two sides to the bathroom connected with a shower in between. There's a door into the shower from both sides, but on one side it opens the "wrong" direction so that you'd have to sort of climb over the toilet to enter from that side. Obviously, we just entered from the other side that was easier, but it was odd; and the shower door did not fully close so it was easy to get water outside the shower onto the floor. There was a little bit of mildew/mold in the corners, and there wasn't any shelf or shampoo caddy to put things on in the small shower, which would have been helpful. The shower faucet and sink faucet in the bathroom turn on opposite ways (push one/ pull the other). Not bad, just odd. Also, there was no garbage can in either side of the bathroom. So if you needed to throw anything away from the bathroom, you had to walk down the hallway to the kitchen. The kitchen is very small but we didn't really use it, so that was not an issue for us. The living room is pretty big. It was nice to have a washing machine and drying rack. The bedroom is quiet and dark, very good for sleeping except that the pillows unfortunately were really uncomfortable.
Overall, we had a really great stay and the pluses definitely outweighed some of the small negatives. We certainly would recommend it based on fantastic location and our very outgoing and helpful host.