The official availability date for the G1 is slated for Oct. 22. If the G1s begin arriving on the 17th, that will be five days ahead of schedule. Not bad, T-Mobile!
T-Mobile hasn't provided any information about whose G1's are being shipped. No know knows if the orders are being processed in the order they were received, or if T-Mobile is choosing to send out batches of phones to certain areas of the country.
Either way, it makes sense that T-Mobile is moving up the availability date. Since HTC and T-Mobile tripled the original number of phones that are going to be available over the next couple of weeks, they likely wanted to get some of the additional cartons of inventory out of their respective warehouses.
Welcome to the world, G1.