Sonia's place was exactly what we were looking for. For us it was all about the balcony. Even though the weather was a bit chilly, we spent a good deal of time out on it, both before and after our explorations of Rome. The piazza is a beehive of activity almost 24hrs a day. I never imagined I would spend so much time watching the "take down and clean-up" of a market - but it was absolutely fascinating to me.
As others have mentioned the location is ideal in more than one way. We stayed 4 weeks, and loved picking up fresh ingredients at the market and stores just outside the door. Moreover, it is so centrally located that any walk we took lead us somewhere remarkable.
I was initially worried about the stairs because I have a bad knee, but they are level and are not steep. I was also relieved to find a handrail on one side.
Someone previously mentioned that the pictures did not reflect the apartment. The only differences in our opinion, were positive ones: the red and white bed cover and wall thingy was gone (I was seriously happy about that), there are nice prints on the walls, and a newer sofa. There is also a large mirror now on the wall between the balcony doors and the window. The table is now in front of that, next to a good sized fridge and freezer, and a small cream-coloured cupboard. The sofa is now along the side wall. For us the furniture arrangement worked really well.
We can definitely recommend Sonia's place, especially if you want to feel connected to the heart of Rome.
p.s the self check-in was also super easy, Sonia gave us crystal clear instructions.