I am going to order mine at apple.com next Friday and get it a few days later by post.
Not sure how folks will sell a phone that requires a T contract on eBay, but I am sure there is a way.
With 100M+ iPod units shipped under its belt, I bet Apple will be prepared with a decent supply on Friday.
The 29th is going to be quite a day!
Best,
Kurt
edit: Informative new video from Apple:
http://www.apple.com/iphone/usingiphone/guidedtour.html