Fun fact - Apple doesn't currently support iMacs with the Fusion drive. If the drive dies, their only option is to replace the entire machine. I would say that this is definitely screwing early adopters.
Replacement hybrid drives are not available in their internal support inventory system yet, so they can't swap out your dead drive at the Genius Bar, or even via in-home technician visit.
If yours dies right away like mine did (3 days in, so I got to spend many hours moving data and configuring before it died) and it's a custom build from the online Store, don't bother going to a Genius, just call AppleCare and have them order you a brand new machine. I think most machines with Fusion drives are custom builds anyway, so this probably means everybody who has a Fusion is in this boat.
Absurd, but true - they do not actually support their most expensive current machine; my guess is that they are bogarting all the hybrid drives they can get for manufacturing, and will provide them to repair after the lead time on machines gets lower, but that's cold comfort to their early-adopting loyal customers.