I think I have found the best use for my miles :-)

The future mrs gdaily is living in Ukraine, and she needs to get a visa for every trip/country we visits. The problem is that she needs to show a return ticket when applying for the visa. And it is not 100% that she gets the visa...

So I book a refundable ticket with miles, she applies for visa showing this ticket, and if she gets the visa, we cancel this ticket and buy her a cheapo ticket instead.

For my self, I have used miles mostly for upgrades to biz on long flights.