DH and I spent one night there celebrating our 3rd wedding anniversary, so this was back in 1978. I believe at that time our room was $135/night. Now it is much, much, much more than that.
We had a room at the back of the hotel, so no view.
It was very oddly decorated, at least I felt it was. Stripes, flowers, prints, etc. But we weren't in the room much. We were out enjoying the island, and the hotel. It was wonderful sitting in those nice rockers on that long, long porch. The grounds are beautifully decorated.
The hotel is lovely, very...well, grand.

When we were there all 3 meals were included in the price, and they were wonderful, elaborate meals in the lovely dining room with servers in jackets. Dinner was an event. Ladies had to wear pant suits or a dress, men had to have jackets. They had a full orchestra playing. It was awesome.
I would love to stay there again, but it's just too expensive. Maybe a package wouldn't be as bad. They offer several weekend packages throughout the summer. Just google "grand hotel, mackinaw island" and their website should come up and there you can find their room prices and package deals.
I have to say it is awesome staying overnight on the island. Once the last boats go back over to Mackinaw City it gets much quieter and way less crowded. Just hearing the horses clip-clopping on the street, and no cars, it's really a neat experience.