Wonderful experience all around. My party included my baby and my mother. The apartment consists of two bedrooms, a large living room, small kitchen and bathroom (shower only). Historic touches are present throughout. Two air conditioning units are provided as well as a floor fan. However, as all the windows (which are actually doors) open widely, I opted to let the fresh air come in as a light breeze.
The apartment proved to be a lovely respite from the heat and the bustle of the city, a place to cool down and recharge before heading back out again. Located on the southeastern edge of Trastevere, the building felt safe and was centrally located to not just the shops and restaurants of the neighborhood but the other central historic and tourist sites in Rome. There are a handful of drinking and eating spots immediately below the building as well, in case you don't feel like venturing far.
Walter, along with his co-host Marco who let us in, were communicative and friendly. Walter went above and beyond by offering to arrange car service to and from FCO airport, which I gladly took him up on.
I highly recommend this apartment and host.