It's a total PITA. On this continent, it's handled by Althon Micro, located in Canadistan.
You have a 2 year warranty, email Sapphire, wait a LONG time for them to respond (but once they DO respond, communications becomes almost instantaneous), ship it to Althon with some sort of ($15-25 seems to be normal, a friend just paid $15, the intarweb usually says $25) fee so they can ship it back to Taiwan, wait a REALLY LONG TIME, receive no communications from Althon, and one day a video card randomly gets delivered to your house.
I know a few people who have done this, and it sucks every time.
In other words, Sapphire's RMA is nice - but the company they outsourced it to sucks.