From the product page:
Not exactly simultaneous multi-card recording, so I assume that means no protection if the primary media (the SD card) fails during a take or before the sound files have finished copying over. But it’s most of the way there.
Personally, the stakes on my shoots aren’t high enough yet, so the auto copy feature is good enough to me – the MixPre-6 having no redundancy at all made me hesitate to even consider it. After waiting for reviews and demoing it, I’d imagine this thing will be on my upgrade list, as a good stepping stone between where I’m at and the 633. Even then, would be handy to keep around as backup and a lightweight setup.