Other guests' reviews cover most of the points, but let me list what I feel is special about David's place.
1) Hospitability
David is genuinely hospitable, which I think is the important element for being a host. I chatted with him for about 15 minutes, and had a very good impression as a person.
2) Flexibility
David is really flexible, which makes things easier for the guests. It's good that he can cater to the guest's needs without any hint of unwillingness.
3) Elegance
You can get to know his sense of beauty by the decoration of the place. It feels good to stay at an elegant room.
4) Restaurant in the same building
I recommend the Italian restaurant in the same building. It was the best
seafoods I had in Milan. No worries for drinking white wine a lot and getting wasted, as you can get to the room in a minute.
I want to come back again.