My wife, 14 month old son, and I stayed at Marco's this past weekend. We stayed 3 nights and 4 days total and loved it.
The location is perfect. Theres a great place to get coffee, pastries, and pizza right next door called Molino Bakery Bar and cucina, and a great place for gelato right across the Piazza. Directly across the piazza theres a supermarket that has everything you need.
The living room has a great view of the from one window, and the piazza from another. The bathroom is very small, and shower sometimes annoyingly small, however it definitely did not detract from the stay. Its understandable since the building is very old. We had no issues with hot water at all. The bedrooms are a good size and beds are comfortable. My wife thought the pillows were incredibly comfortable and I agreed. Flaviana was nice enough to set up a pack n play in the other bed room for my son and he slept well in it.
The apartment is on the 4th floor which is great for a good view, but a good work out walking up the stairs. There is a very small elevator to bring you up which is great but it only fits about two people comfortably.
Marco and Flaviana were very easy to communicate with and Flaviana even let is come by to pick up the keys well before check in time. She gave us a map of the city and gave a very detailed explanation of all the areas of Rome and what to see.
We couldn't have asked for a better stay in Rome and it was worth every penny!
Also if you're a runner, the apartment is well within a good running distance to the Colosseum and back as well as many other important areas.
Thanks Marco and Flaviana!