Marina is fantastic and is a very gracious and helpful host. The flat is exactly as described and conveniently located. There's a 24 hour grocery store around the corner and you can easily navigate the city on foot.
We opted to take the train from the airport. Having used trains and subways in many cities in America and London, we felt comfortable opting for public transportation. We figured it out and arrived without incident. However, if you have the extra money available and are not fluent in Italian, let Marina arrange a driver for you. There aren't maps on the trains and it is a little more difficult to figure out than the train systems in other places.
My favorite thing about the flat was the bed. It was insanely comfortable! The flat itself was a little more noisy than we are used to as sound travels easily between the flats. However, everything quieted down at night and we rested well.
I'd definitely recommend staying with Marina and am grateful to have had use of her flat.