I ordered mine on Saturday (May 30th) once I could finally register for the site using my Sony Card info. I've heard mixed reports from different buyers and even different Sony Rewards/Card people. Once you've registered for a new Sony Rewards account using your new Sony Card info, it seems like you simply need to add the PRS-505 to your cart and check out (making sure your points purchase on the Sony Card is $299 or greater.
My early post in this thread has some more specifics if you missed it.
Good luck!