We stayed for a week in the unit and we had a great time. The 2 AC's were very useful during the hot days we had. The wifi connection worked pretty well every day (only one day it was particularly slow but I think it was a general issue in the area), which allowed us to keep working while we traveled in Florence.
The apartment is located very conveniently, close to the most touristic attractions but still in a quiet street. Great bars and restaurants around.
The sofa-bed was pretty comfortable and we used the washing machine a couple times, everything worked perfectly. The kitchen is fully equipped, though we didn't cooked.
The apartment is in an eighth floor, only accesible by stairs, that's something to have in mind if you have any moving difficulties or are in a wheelchair.