I spoke with Amazon.com today about their guarantee of delivery of Harry Potter and the Deathly Hallows by July 21, which is Saturday. I pre-ordered HP for my wife on Sunday, which is in time for the guarantee, and I received an e-mail letting me know my pre-order was being readied for shipment via UPS. Then I remembered that UPS doesn't usually deliver on Saturdays! So I alerted them to call me (they have this very tight new technology that has them call me when I'm ready ... now ... in 5 min. ... in 10 min. ... in 15 min). The nice voice on the other end of the phone assured me that Amazon had a special arrangement with UPS to deliver Harry Potter and the Deathly Hallows to readers this Saturday as promised. So in case you were worried, it's been taken care of.
To try their Amazon.com's call technology, you need to go to Amazon Help and look for the Contact Us box on the righthand side with the Customer Service button inside. You'll have to log in. Let me know what you think.