Federico was a fantastic host, and he provided some really great tips on the best places to go in the neighborhood. He's super responsive, and even sent me detailed directions on how to get to the flat from the airport.
The flat itself is very conveniently located in Trastevere, surrounded by amazing restaurants and bars and shopping, all on cute little cobblestone streets. It does get a little noisy at night (there are a couple universities in the area), but earplugs are sufficient. It's right across the river from most of the major attractions -- about a 15 minute walk to the Pantheon. It's also right by a taxi stand and bus stop.
The bedroom and kitchen are quite spacious, and the kitchen has knives and pots and pans for cooking. The washer/dryer worked very well and came in handy since I stayed for about 1 month. The flat gets almost no sunlight at all, which is perfect for folks who like to wake up late :)
Important to note that the main way to access the kitchen is down a very narrow spiral staircase, so if you have mobility issues it may present a problem. Otherwise, look forward to getting a good workout on your way to and from the kitchen. Earn that pasta!