Update: Snap, our update failed out. Like four times. It didn't brick the Kindle but it sure as hell killed all our e-books and now the device says it's got no remaining storage. Thanks! More after the break.
Update 2: Ok, we just got off the phone with Amazon support, they're claiming the update was released too early and isn't the "real" update which is supposedly due out later this week. (The email that notified us of the update did mention it would be available Friday.) We're confirming with Amazon corporate what the hell is going on.
Update 3: Alright, final update: the update IS supposed to be out as of today, but Amazon's page has changed to describe this as more of a rolling process for users over the next few days. (The direct download link is also gone now.) Our update finally took, and we haven't really seen anything much different so far.