We stayed there on our way back from Texas with the GS-DP. It is as described. You can use the hotel's ammenities such as pool, spa, game rooms, excercise rooms etc. Take in the "old time shootout" at the depot before boarding the train in the morning for the GC.
One word of advice, buy the air conditioned car tickets ($5 more per person) and inform them that you need to be seated in the forward most AC car. The ride is quieter, smoother, cooler and you will thank me for it later as the rest of the cars that are not air conditioned become noisy, sweltering, smelly examples of a train in India or Pakistan.
You can take a free shuttle to some of the South Rim's hot spots and they will get you back for the return trip home on time.
If you are wondering about that crazy clear glass cantilevered walkway/bridge, it is on the North Rim and is on Indian land. It takes a long while on very poorly maintained bumpy roads and costs a lot to get there, can't be accessed with small cars or RVs and costs to go out on plus you can't take cameras, cell phones etc while out on the walkway/skyway.
The rest of the canyon is a great trip. The rail trip has some surprises on the return route and I won't spoil them for you.
I can say that when we went, we saw a mountain lion about 30 yards from the train that was chasing some prey. It was magnificent and VERY BIG!
Enjoy.