Thought I would provide some comments on this excellent hotel as we are coming to the end of a 4 night stay (which was booked on points about 8 months ago - availability is limited).
The booking was for a base room which is listed as having a “land view”, and limited other information online. I had enquired in advance about a paid upgrade - was quoted €400 a night for a 2 category upgrade to a room with private terrace and hot tub, so declined. Was really just glad of using points to visit Mykonos in peak season - the base room itself was selling for up to €500 - and was fully expecting to receive this as the hotel was sold out, and no complimentary breakfast as a Design hotel.
However, the staff were almost falling over themselves to be helpful at check in. The front of house manager came over to introduce himself, repeatedly apologised for only having a limited upgrade to a sea view room available on the first night, and said we could have breakfast for free throughout our stay, and he might have another room available from the following day. We thought no more of it - we did not really want to bother with moving rooms as the one provided was more than nice enough - until one of the concierge team came to find us at breakfast to say they had another room available, which we were too politely British to decline.
We ended up moving to a really stunning room - exactly the one quoted for the paid upgrade, with a large private terrace looking out over the sea and the windmills. Drinking champagne from the hot tub while watching the sunset certainly made the room change worthwhile.
It may have helped that there was some additional confusion at check in as they thought I had two rooms booked, seemingly due to a Marriott system issue. They confirmed Marriott had paid them for two points rooms (which I assume will be close to full rack rate for a maximum occupancy hotel), but I had certainly only been charged the points for one!
The rest of the features of the hotel are well covered by the many positive reviews on tripadvisor - great pool, good restaurant, walking distance to town. And it seems to have a small army of staff running after every guest, all very friendly.
Overall, very highly recommended.