David's Milan penthouse was a dream. It's in a very central location that is only a 5 minute walk from the Duomo, about a 10 minute walk from all of the finest shopping, and about a 20 minute walk from Sempione Park. The apartment is impeccably furnished, and has every amenity we needed (including a top notch espresso machine). David and Dario were so easy to communicate with and provided wine, snacks, and some wonderful local tips when we arrived. We couldn't have been happier with our stay.
One tip: If you are planning to drive to other parts of Italy before or after your stay, I recommend picking up your car once you leave Milan. Driving in Milan is not for the faint of heart and non-residents cannot drive into the central parts of the city without purchasing a pass (which I wasn't exactly sure how to do). Regardless, you don't need a car since cabs/Uber are plentiful -- there is a cab stand near the Duomo -- and public transportation is very easy!