Victoria, British Columbia, Canada
I am a fan of Diners Club for using Club Rewards points to keep airline and hotel accounts active. Case in point is my wife's Air Canada Aeroplan account. The Aeroplan website had a notification warning my wife that her miles would be deleted on April 13 if there was no account activity. She also received an email warning. This is good customer service to give advance warning before simply deleting miles.
April 2007 we had a flight on United to Las Vegas and inserted her Aeroplan number in the reservation. Now, a year later, I needed to get some account activity and I transferred 1,000 Diners Club Rewards (the minimum transfer allowed) to 1,000 Aeroplan miles.
I made the transfer on April 2, 2008 and hoped the miles would register in the Aeroplan account before April 13. I decided to check today to see if the transaction had gone through. The website stated 2-6 weeks and my wife has too many miles to let expire. My fall back plan was simply to buy Aeroplan miles.
The Diners Club transaction posted 1,000 Aeroplan miles on April 4, 2008. The process was completed in 48 hours.
I use my Diners Club primarily to top off frequent flyer accounts for premium awards. There is a $0.95 charge per 1,000 points transfer. It is a small price to pay when 20,000 points exchanged for 20,000 miles can mean the difference between an economy award flight and a business class award flight (although the differences between economy and business or business and first tend to be more in the 40,000 mile range these days for most airlines).
Starwood American Express is also good for airline transfers, however, I find the Starpoints much more valuable as hotel points than airline miles, even with the 25% bonus on transfers of 20,000 Starpoints.
I use Starpoints for extending the miles in frequent flier accounts where I have had no activity. I have Mexicana miles I have been holding since 2002 (how I wish I had redeemed this two years ago when the redemption options would have allowed a First Class ticket to most anywhere in the world from the USA for 100,000 miles) and each year I simply transfer 10 or 100 Starpoints to Mexicana to extend the mileage expiration.
SPG Platinum members have no minimum transfer requirement for Starpoints to airline miles. Gold members have a 1,500 Starpoints minimum transfer and non-elite members have a 2,500 Starpoints minimum transfer. That is why I like the Diners Club card since 1,000 Diners Club points to airline miles is a transfer option I favor over spending 2,500 Starpoints from my wife's account.
We can better use 2,500 Starpoints for a Cash and Points hotel room or a free night at a category 2 hotel on the weekend. (Technically, 3,000 points for SPG Category 2 weekend award night, but as a platinum member using an award booked with my wife's points, I get 500 points back as a platinum amenity and therefore 2,500 points for a weekend stay.)
The Diner's Club card is expensive at $95/year, however, for loyalty travelers the Club Rewards program offers many hotel reward options using Club Rewards points that are not available with SPG AmEx (although a regular American Express Membership Rewards card does have hotel transfer options).
Diners Club is a useful card to have for the exchange options of points into airline miles or hotel points.