My wife and I spent our wedding anniversary here, for it's great location and past experience with Park Hyatt.
The check-in process was unpleasant; when making reservation, I requested "suite upgrade" but was told it's a two-twin-bed suite. When checking in, I told the front desk we were here for 10 years anniversary and would like to request a king-bed suite, but told it was unavailable. We checked in the room, and very disappointed -- not only it's a two twin-bed suite, it faced "mountain" and another apartment. In case you missed it, this hotel is great because it is right on the beach; if I cannot see the ocean, why staying here? I went back to the front desk to complain -- and got a different answer from a different person. I was told there WAS a king suite facing ocean available right in the same floor, but I need to pay $50 USD more per day. I took the offer, and stated my disappointment of ill-informed situation and ill-arranged room in the first place.
Maybe Hyatt only pays attention to its elite members, which I'm not???
Besides the check-in issue, I found the hotel staffs seem sometimes unfamiliar with some basic routines or some simple questions we had. To think about it, it may be because it's a new hotel (open in early 2013?)? But don't get me wrong, the service was generally very good.
Other than the staffs issue, I really don't get all the fancy lighting and switch in Park Hyatt -- it's very annoying to wait for couple seconds before the lights start to dim when trying to turn off the light.
I probably will come back to this hotel for the great location and the great view (if they can get the room right next time). However, I'm getting disappointed at Hyatt's general customer service; I guess I will try to stay with the program that I have elite status...

We recently spent two nights at this hotel. It is lovely, brand new, views are spectacular, rooms clean and luxurious. However overall we had just an okay to poor experience. It started with the van from the airport we had arranged through the hotel. It took almost two hours in traffic to reach the hotel, with a driver who seemed very inexperienced which made the trip much slower than necessary. The location of the hotel is also not at all what I had expected. It is billed as being at the famous Haeundae Beach, but isn't even within walking distance. We had to take a taxi the next day which was a big disappointment. Next we checked in, only to be told the refrigerator we had requested with our reservation, six months in advance (before the hotel even opened) and confirmed a month before our trip, was not available. Since I have dietary issues which require me to bring my own food this was unacceptable and not a good start to our stay. The staff solved the problem by removing all items from the minibar in the room so I could use that fridge, but it was annoying to start our stay with yet another problem. I also mentioned at this time that I would require freezer space for some of my food and the staff looked at me like I was crazy (big difference from the Marriott Courtyard in Seoul that we had just left after 5 day stay, where staff were incredibly helpful). I felt very unwelcome in this Hyatt hotel which made me very uncomfortable. Next we checked into our rooms (2) and the king room absolutely reeked of perfume. I could not even stay in the room for five minutes. No idea why this was true. Hotel staff also seemed clueless as to how this happened. They offered a room air purifier but it was obvious that would not solve the problem it was so severe. At this point, I was ready to leave the hotel, but management stepped in and move us down the hall to a suite. The suite was spectacular, although had twin beds which I thought was weird since my husband and I had requested a king room. But we took the suite anyway, since it offered more space and we had four adult children with us so two of them could stay on rollaway and the sofa in the living room while the other two shared the second room we had booked. The rest of our stay was pretty uneventful. The concierge did arrange a driver for us for the next day, who turned out to be wonderful. Although he didn't speak English he did get us where we wanted to go and to an unexpected boat ride, so that was cool. Mostly, however, the hotel staff bowed a lot, but when we actually needed help with anything, we felt they were not really helpful. Every time we requested something, it seemed we had to wait a very long time for it to happen.Their English comprehension was very lacking which in a supposedly world class hotel was annoying. The hotel was very expensive. Brunch for example, was $90 PER PERSON!!! It looked lovely, but we didn't eat that. Overall, we would never stay here again and wouldn't recommend it.