I stayed last month in the Hyatt Mainz for the first time. I was able to use a suite upgrade certificate. The hotel is very nice, especially the location near the river. I received some fruits as amenity. Lounge access was granted without any problem. Wife and myself liked the lounge very much - nice ambience.
The atmosphere in the restaurant is very nice with the open cuisine. Unfortunately, I didn't like the food and beverages. Nor did my wife. But that's only our personal taste. Additionally, service was very slow.