I do not gamble so I cannot speak about the gambling facilities. This review is only in regards to the crab legs/prime rib dinner buffet held on Fridays.
This was my first buffet experience at Ameristar and it was great! I went with some friends and my sister (who is a pescetarian - vegetarian + seafood only) and there was a great variety of food for all. The crab legs were great, the prime rib was really not (the main thing holding off from a 5 point review) but that's ok - plenty of other stuff to eat here.
The service was excellent and our waiter cruised by every few minutes to check on us.