We stayed in Paolo's appartment in Trastevere for 3 nights around New Year's Eve. It's superbly located on the heights of the district (lots of steps, but not a problem for us), within walking distance (+/- 5minutes) to the best bars and restaurants. There's a small market square just down the street, and lots of little shops packed with amazing products. The central highlights of Rome, such as the Pantheon or the Forum are 15-20 minutes by foot. Getting to Termini is easy as well, with tram and bus stations close by (+/- 10 minutes).
The flat is cosy and perfectly clean. The small kitchen is well equipped, and the beds (one normal bedroom and one sofa bed in the living room) are extra confortable.
Paolo was flexible with our hour of arrival and gave us maps and advice on things to see and do during our stay.
We liked our stay in Trastevere a lot, and would definitely recommend this place !