My mistake I thougt they were using something advanced, not just a half arsed rip off of ReadyBoost, which has been around since Vista.
Which ever way, it's not innovation, unless you count copying as innovation. But it's Apple so that doesn't matter.
You could hot swap a ReadyBoost drive since it was a simple swap (cache) unit. Fusion drive doesn't replicate data from hard disk. Instead, the capacity of a Fusion drive is a sum of HDD capacity + SSD capacity.
Intel Ultrabooks have small SSD drives for faster reading/writing but the space is wasted for caching instead of adding capacity to the overall storage.