We would highly recommend Ekaterina's apartment in Trastevere. It's centrally located with cafes, restaurants, a laundry, supermarkets, trams and the river all within a couple of minutes walk. It can be quite noisy at night because it's right on the Piazza Santa Maria but it didn't bother us - just buy some earplugs if you are a light sleeper.
Ekaterina has taken so much care with the place. Thoughtful items like body wash, coffee pods and biscuits were all provided. She even left us with fresh flowers. Thanks Ekaterina!