When I recieved my unit a few days ago, it was NOT preregistered. "My Kindle Devices" page showed the PW without a serial number.
I registered the unit through its own registration screen. It did not appear on the "My Kindle Devices" page. On the Order page it showed "Still Shipping."
I called CS. First they told me it could not be used until the official delivery date of Oct 11. I appealed to the next level.
Then it appeared on "My Kindle Devices" page as a SECOND PW with a serial number. I deregistered the non-serial number unit.
Everything is fine now but there is a possibility I may receive a 2nd unit which I will have to return. It now shows as "Shipped" on my Order page with the proper UPS tracking number.