Programs constantly change for Diners. They used to be really good because they had a ton of programs, but lately they've lost some popular ones (like United). Also you used to be able to transfer from your FF program into Diners, but I think we have that option anymore.

Honestly, if you have to pay for the $300+ annual fee yourself, I'd suggest joining a FF (airline or hotel) credit card program. Annual fees are usually between $35-85.