I've stayed at JW Marriott in Grand Rapids twice for business, with a 1 night stay and a 4 night stay. Of the hotel options available in Grand Rapids, the JW is the by far the closest to "5 Star" possible. It is also the most expensive option, usually an average of $40-$50 more per night compared to the Amway Grand.
The JW scores high marks on the rooms, comfort of bed, cleanliness, bathroom layout with individual shower stall and separate bath tub and my favorite amenity which is a nice bathrobe in the room.
The food options at JW are "ok" and typical hotel expensive. 616 which is the main restaurant at JW is one of the better restaurants in Grand Rapids with a wide variety of food. Room service options were surprisingly disappointing with no pasta options available but still having the usual hotel fare (burgers, club sandwich, salads, etc). The lobby bar called Mixology is very nice especially in warm weather as there is an outside patio.
The fitness center has very updated equipment with TV's at each cardio station - however the room is a bit small for the size of the hotel and it likely gets busy at peak time. There is also a spa connected to the fitness center, which I did not use.
Overall service from check-in to wait staff to valet attendants and the staff at the Starbucks off the lobby were very professional and in nearly every instance refer to you by name.
Overall a fine option when staying in GR - just be prepared for the high end on price.