We enjoyed our stay in Carlo's apartment. It had everything we needed for a nice stay, we could even cook because the kitchen was fully equiped and even has a dishwasher. The bed is very comfortable and you don't hear the street noises in the apartment. As we were there in winter a working heating system was needed and that it did well.
The apartment is localised on the less crowded side of the Tiber, so after a day with crowds of other tourists and locals we enjoyed coming back to a bit more relaxed area. But it is not boring there, there are a lot of nice cafés and restaurants in walking distance and Trastevere is just a great place to be. The big tourist attractions could easily be reached by foot.
We would recommend a stay there :-)