I have stayed at this Park Hyatt twice in the last year. Both stays were extremely pleasant and as a diamond member, I was upgraded to the corner respire room, which is much larger than the standard room. It appears that they haven't updated the furniture in this hotel since the mid-90s and is soon due for a refurbishment given the price point though I do believe that they have replaced the furniture in the suites.
Service is good but not as good as competitors such as the St. Regis where you are welcomed with champagne, led to the elevators by a receptionist, and shown around your room. In addition to this, I found that turn down service at the Park Hyatt to be subpar. It's nice that they leave the water bottle and glass by your bedside, but what happened to placing a small something such as a piece of chocolate?
Breakfast was included as a diamond member and I highly recommend the restaurant, NoMI. Breakfast was delicious, my favorite being the health shakes in the morning -- the 'greens' shake was my favorite.
Overall, nice hotel and would definitely return if the price is right.