Boy Genius Report has an AT&T memo regarding their iPhone 3G policies. Here’s an interesting bit on activation, which suggests that it might be possible to do most of it at home:
The new 3G device will be activated in store in both AT&T and Apple stores. Customers must accept AT&T and Apple Ts & Cs, sign a 2-year agreement, and select the data plan for the iPhone 3G before leaving the store. The current iTunes activation process will no longer be required for iPhone 3Gs, however a short tether process to unbrick the 3G device will be performed in all AT&T stores (tether cords will be provided). Apple stores will also perform this tether process, however in the event that a customer’s device is not tethered in the Apple store, their device will be inoperable until they get home and tether through iTunes. Prepaid and Pick Your Plan will not be allowed on the 3G device.