I pre-ordered a white iPhone 16GB from my local AT&T store on 7/22, it arrived at store on 7/24 (fedex overnight).
So the availability crunch may be over.
Check the above link for some key tips on the process. The promised email notifications never got to me. I only found out the phone was in because I was checking the status page, and because I'd figured out that I needed to enter the store's zip code, not mine.
As usual the AT&T staff have done well. For an evil company AT&T has quite good front-line staff -- at least some of the vast amount of money I send AT&T must be going to the employees.