I have been using a Diners Club MasterCard for many years now, in no small part because the points I earned from it could be transferred into Amtrak Guest Reward points. The three cross-country train trips Lisa and I have taken were on DC-to-Amtrak point transfers. I was considering using those points to go to SMOFCon in Chicago this December, and went to look up how many points it would take to buy a bedroom on Amtrak (about 110,000; I have about 15K banked right now), and then I went to Diners Club to see how many points it would take to buy the Amtrak points. It was then that I discovered that Amtrak had discontinued its partnership with Diner's Club at the end of 2015. Had I heard that, I would have dumped all of my Diners points back then and could probably have taken the trip. As it stands now, I have a bunch of DC points "stranded."
That actually significantly reduces any incentive to keep using the Diner's Club, which heretofore has been my primary credit card. I may dump all of my points out of it into IHG (still a partner), where it would be worth perhaps as many as eight free nights, use the nights on our road trip to Kansas City, and cancel the Diner's Club card once I reprogrammed all of my automatic payments to use one of my other cards.
I guess I'll have to go ahead and apply for an Amtrak Guest Rewards Visa and start accumulating points over there. The annual fee is lower, too.