I stayed here with my mother for 5 nights in July and we had a great stay in Rome.
Simone wasn't able to meet us, so we instead met with his father Roberto, who showed us around the apartment and answered our questions.
PROS:
The apartment is ideally located and we were able to walk everywhere (including 1 hour to The Vatican City!).
The space was just perfect for our needs, with a fully equipped kitchen. Having the second bed in the loft area was great for me and my mother.
Communication from Simone before the trip was great - I was sent a map with directions from the train station and he was able to answer any questions that I had.
We were given two free transport tickets and an Italian mobile phone (although we didn't end up using these) as well as a small bottle of wine in the fridge. These small touches added a personal feel to our welcome.
CONS:
As a few reviews have mentioned, there is a market outside the front that sets up from 5.30am and the noise does wake you up. We used this as an excuse to get out and about early and come back early afternoon when the temperature was at its highest, but we did get quite tired after a 5 night stay!
As two females, the area around the apartment didn't feel that safe to us - there were a lot of men who sat out in the street at night and would make comments to us both as we walked past - this made us feel a little uneasy.
The cleanliness of the apartment was not as expected as per the photos - the walls were grubby, the upholstery was stained and the shower had a fair amount of mould around it.
Unfortunately the air conditioning was not working when we were there, but perhaps this has been fixed now.
Another point to mention is that the hairdryer was not very powerful (it's the kind you would find in a hotel that's attached to the wall with a cord) so I would suggest that ladies would bring their own one if they have long or thick hair and don't enjoy going outside with it wet!
Overall I would recommend the apartment for a basic stay in a good location with a helpful host.