Location to the airport.
I paid for my room on Kayak when I booked the riom. When I arrived the girl at the desk told me there was no way I paid online. I was ready to leave and she caught me and said she received payment thru Kayak. Then she sill tcharged my credit card. It is now 10 days later and still they have not refunded my money for the second charge and have never even offered a discount or anything for their mistake.