I was lucky enough to attend the T-Mobile G1 product announcement in New York a couple of weeks ago and actually pre-ordered my own G1 that day on the train back to the airport for my flight home and it turns out it was a good thing I did. I read reports earlier this week that T-Mobile may have sold out of the G1 and just received confirmation and more details from my T-Mobile representative. T-Mobile did indeed sell out of the original stock even after nearly tripling the number of phones available for initial delivery.
T-Mobile is now letting everyone know that you can still pre-order the device from now up until 21 October prior to availability on 22 October. I understand that those who ordered before 3 October will get their devices on 22 October and those who pre-order up until 21 October should get theirs on 10 November. I also read on The Boy Genius Report that Best Buy Mobile stores will carry the T-Mobile G1, but it won't be released for sale until 16 November. Thus, it seems your best bet for picking up one of these is still to pre-order through the T-Mobile G1 website. I also saw them starting to appear for crazy prices on ebay, with none actually being available until 22 October.
I also asked some questions regarding my family text messaging plan and I was told that my best strategy would be to buy the least expensive G1 plan with 400 text messages and I would still be covered by my family plan unlimited text messaging plan so the 400 really means nothing. This is actually what I did when I pre-ordered because I figured I could always upgrade to unlimited messaging if my family plan didn't work out.
T-Mobile also confirmed that I wouldn't be able to use both my BlackBerry Curve and T-Mobile G1 with the same SIM card because of the BlackBerry Internet Service allocation that comes with a BlackBerry plan. I am a bit bummed about this since I really do like my BlackBerry Curve, but hopefully the G1 exceeds its functionality and I won't have to go back to the Curve.