I can't believe you guys are even debating this. It's spelled out on Apple's website in plain English.
Apple - iPhone 5 - Where to Buy
Apple Retail Store
Buy iPhone 5s and iPhone 5c at the Apple Retail Store starting September 20. We’ll help you choose the right rate plan, transfer your contacts, set up your email, and more.
Learn more about buying iPhone at the Apple Retail Store
Apple Online Store
Pre-order iPhone 5c starting September 13. Order iPhone 5s starting September 20. They ship free and ready to use. And you’ll find a wide range of accessories to complement your iPhone.
Learn more about buying iPhone at the Apple Online Store
As annoying as it is you have to wait until the 20th to order a 5S. I'm at least hoping you can order at midnight and then pick up from a local store so you're guaranteed to get it on release day. Otherwise if you're planning to order online you're waiting at least a day for it to ship to you.