What a FANTASTIC apartment this is! We absolutely loved it - it's aesthetically gorgeous, has very nice and well-functioning amenities (the bathtub - with jets - is sooo divine, beautiful rain shower, lovely and functional kitchen), and is in a great and well-located neighborhood full of cafes and restaurants nearby. The beds are incredibly comfortable (the best we slept in during our 5 city Italy trip - and the master bedroom bed is a true queen size rather than the two single beds put together... bonus!), the apartment is super quiet, and can be made to be very dark, which made sleeping so wonderfully easy.
The only things to note are that there are indeed a lot of stairs leading up to the apartment, so if you have knee troubles or other physical factors, this could be an issue... the fact that it is a fourth floor apartment does ensure that the apartment is quieter than a street level apartment would be, though, and it allows for a really lovely view of terra-cotta rooftops and distant hills. There is also the beautiful feature of exposed beams in the master bedroom, which give the room such a gorgeous look, but you'll want to watch out for them if you are tall. :)
We really enjoyed talking with Benedetta when she met us at the apartment... she was very sweet, and had even stocked the kitchen with a few groceries (yogurt, milk, granola, coffee, and a few other staples... and a bottle of wine!) which was a huge help for us weary, hungry travelers!
We would highly recommend this apartment, and hope to be back again someday!