Leonardo's flat was perfect for us. It is ideally located in Scheunen Viertel, a great district to hang around : cool shops, restaurants and cultural places. It is also very close to other very nice neighborhoods (Prenzlauer Berg) and a 20 minutes walk from the center (but it's 5 minutes away from a subway station if you don't want to walk).
The place was welcoming, well-equipped, clean and ready for us. We didn't meet Leonardo, but getting the keys was very easy.
We recommend the place, it was part of our lovely summer holidays in Berlin.