Per the Kindle update page:
We know Kindle customers are anxious to receive the 2.5 software update, so we wanted to provide you with some details about its status. We've rolled out the 2.5 software release to a set of Kindle customers and have received great feedback from these early customers. Based on this feedback, we are making some small adjustments to improve the experience further. We will be rolling out the 2.5 software update to more users over the coming weeks.
Nice work (not). Off goes WN until I hear a LOT of people are getting it.