cash back is a good option....if a customer prefers cash, I can do that - however, I also offer travel gift certificates instead of miles so a savvy customer can get 'cash' credit *and* earn miles.

we have a really neat plan with mortgage points - when a customer meets the conditions of tax deductability for points and wishes to pay them to reduce the rate on a loan (advantageous for loans kept longer than 7 years), we can rebate a large portion of the points back to the customer as their choice of miles, hotel points or travel gift certificates (not cash, to avoid IRS troubles for the customer). This can result in tax-deductable travel.