We loved staying at Apostolos's flat. It was perfect for us (4 adults). The outdoor area was great for a pre-night drink, early morning coffee and anywhere in between. The location is also great - not too far from downtown, but just far enough to feel like you're out of the hustle and bustle! Keep in mind, however, you have to walk up a pretty steep hill in order to get from the city center to the flat (ie. not great for older guests, or people who have trouble walking).
Bottom line: The view is amazing, flat is perfect for a multi-night stay, the outdoor deck/hot tub is very unique and allows you to enjoy the amazing Mykonos weather. Highly recommended.