We had a great experience with Cosimo. He was there to meet us and help with our baggage, and was helpful throughout our stay (He even booked us our cab on the way out of town). The flat was very comfortable and ideally located--walkable to everything, yet withdrawn enough from the main sites that it's not overrun with tourists all of the time.

Only thing about it to know is that it's a lot of stairs; Great for working off that gelato!