it's pretty easy. actually, sites where you can use your rewards are not as rare as skome mentioned... you can use the redemption code (found under Profile section -> Gifts and Discounts) at eBay and many shopping sites. the thing to note is that you'll need to enter the code before getting logging into PayPal when checking out from eBay, while at sites like buy.com you'll enter the code after logging into PayPal at a page called "Review Your Infomration).
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