Demand has certainly exceeded supply. In fact Apple says that while a chunk off the pre-order supply will be delivered to customers starting Friday, many will see their new iPhones until October. Apple did say that there will be some stock available at Apple Retail Stores beginning at 8:00AM local time.
If you want to go that route, you might want to get there early. Depending on where you are, there may be some people lined up already.