Overall: 5-stars, great place for families, large space, fantastic location -- easy walking distance to all major sites. We walked everywhere with 3 kids (youngest 9) and had no problems. Tips from Isabel and the team who rent it were excellent, but I would still keep your guidebooks/Internet, as they cannot know everything (we tried a lot more gelato, for example, than any normal human would try, and in more areas of the city). We saw some reviews that said that there was noise -- we did not find that at all. In fact, the apartment was completely quiet - no street noise of any kind, and rooms can be darkened completely. Air conditioning was among the best we had in Italy. With both units on, it was too cold, and we chose to use 1 unit for 5 days when the temperature outside was 95F/35C.
Things you should know -- these are **NOT negatives, just facts about the apartment that may not be clear from the description** -- we still give the apartment 5 stars: (1) The bathroom pictures are shot with a wide-angle lens, thus the pictures look larger than real life. The main bathroom is small (did not matter to us), and the stall shower in it is about 27" (.70 meters) square, with solid glass doors and a temperature control handle that sticks into the space. We are small people, so it did not present a problem for us, but if you are a bigger person, you will be showering in the second bathroom with the tub (I am 5'6"/168cm and weigh 150lbs/68kg and when I turn around, my elbow hit the temp control every time). Think "Navy Shower" in the main bath. (2) The beds are *very* firm (on an American mattress firmness scale). One daughter had minor sleeping issues for the first nights. After 6 miles of walking or more a day, didn't matter, but you cannot see this on the pictures. (3) Apartment is up one flight of stairs. Cannot remember if the description said this or not. (4) LOVED the fact that windows could completely darken the rooms (cannot see on pictures). (5) No noise at all at night.