I absolutely wanted to experience this Niemeyer hotel and I was not disappointed by the hotel itself, the very intestering building, the beautiful and peaceful location on the lake.
Now, yes it is a bit far from the city but if you want a quiet and nice location, you should chose this hotel.
The main critics I would have would be on one side the service which is friendly but not numerous enough (had to wait by check-in and check-out 20 mn as only one person was at the front desk) and on the other side the restaurant Oscar. While the restaurant room is very beautiful, the food is not really great. The menu has high ambition but the quality of the meal is not up to it. My appetizer, some stir-fried octopus were quite bland and my main course was a very strange combition of fish skewer with canded ginger...
Never seen that before and hope to never see it again :)