This is cool, but I'm not a big fan of "fogging" as a UI tool. I noticed Vista/Aero did this quite a bit.

The fogging just obscures information, but replaces it with something that is distracting. You might get an impression of what's there, but it's a tax to comprehend it. OS X (tend to) do this a lot better - if it's not useful, don't make the user squint at it.

Feels like a pure eye-candy effect with no benefit to the user, but I'd be interested in counter arguments/examples.