We thoroughly enjoyed the first few days of our honeymoon in Antonio's flat in Trastevere. For the price we thought it was a great value and provided a wonderful home base to explore the historic sites of Rome - all without having to rely on taxis or even public transit. Carla (the host, Antonio's Mother) was friendly and readily provided suggestions for dining and exploring. The Bed was so-so, however comfortably slept two adults. To our surprise there was additional room for another two in the living area. Couples or pairs of couples would find this flat a great place to call home for a few days.
The pros:
The number and quality of restaurants and bars
Walking distance to Vatican and Forum
Tiber River Pop-up shops & Restaurants
Carla was super helpful, exactly the kind of host that we needed after a long, sleepless flight from JFK

The cons:
Leaky shower - Carla warned us of this, could use a little attention
Little daylight in the flat (however, if you plan on visiting Rome and staying indoors, then this is definitely not the place for you)
The mattress was not so excellent (again, if you plan on staying indoors this is not the place for you)