Different drivers for both hardware, but sure you wil have same feature (i hope).
Apple has realase compiler for mac osX on X86. In most case just a recompilation is suffisent..
But i think power-pc platform has some extra time: you will need a final cut x86, a high end workstation (it won’t be the first hardware realase of Apple, whoes plans high end computer on x86 for 2007).
So! you have some time before you could use your decklink on a MAC X86 platform! and i think blackmagic guys will be ready then
to provide you a full functionnal driver for your favorite computer.
regards
Oscar