We stayed in Giulio's apartment for 4 nights. It is 10 min walk from Termini station which was extremely convenient for us due to the fact that we visited Pompei (via Napoli) and took the train from the station to Venice. Saves you a lot of hustle and money. It is also very easy to get to Termini station from the airport (express train takes you there in 30 min).
Google maps was helpful in finding the address, but not entirely. We knew the general direction but still couldn't find the house. We had to call Giulio who was kind enough to come to our rescue and get us on the street.
The apartment is on the 2nd floor (European 2nd floor = US 3rd floor) and it looks is exactly like in the pictures. There's a living room/kitchen area and bedroom. Bathroom is equipped with a washer.
We visited Rome in the beginning of April, so we didn't need to use heat or AC, so I cannot judge these.
The apartment was clean, though we had to rewash every single dish we used. Not necessarily because they were visibly dirty, but there was something about them that made us do it.
The shower cabin was pretty small, but I'm pretty sure it's pretty typical for Rome (and judging by our stay in Venice, perhaps the entire Italy).
There's more than enough closet space. The bed was a bit hard for my wife (I was fine, but I like firmer mattresses).
All in all, I would definitely recommend the place.