My girlfriend and I had a wonderful stay at Lisa and Guido's apartment. Lisa, unfortunately, had to be out of town during our visit, so we interacted solely with Guido. He was a terrific host, very courteous and readily available for help and advice. Everyday he would restock a mini-fridge in our room with bottled water and fruit, and he provided us with coupons each morning for a free Italian breakfast at the nearby bar. He also gave us access to the rooftop terrace, which has excellent views of the city. Guido does not speak any English, but my poor Italian was enough to communicate. I appreciated his patience throughout our conversations.
The accommodations themselves are very nice. The bedroom was plenty big for two, and we had a private bath right outside the door. The room also has its own AC unit, which was a godsend during the heat wave while we were there. Their building sits right next to a stop for the 3 and 8 Trams, which are among the more reliable lines, and which can take you straight into downtown. Trastevere is also a beautiful neighborhood to walk, particularly with Lisa and Guido's packet of recommended walks and restaurants.
Overall, I couldn't be happier with our experience. I recommend their place to anyone heading to Rome.