What I wonder is if T-Mobile is lower priority or not-- I noticed the T-Mobile "unlocked" versions were the very first gold iPhones to hit 7-10 days and then October estimates on launch morning. Wouldn't surprise me if they had less allocated to T-Mobile (the Apple store I was in line at definitely had fewer phones for T-Mobile), but hopefully "unlocked" aren't lower priority to locked, subsidized phones in terms of orders placed online. (Given that the hardware is 100% identical to the AT&T model, the only difference being whether it's locked to AT&T).
That's what I'm wondering as well because my local Apple store (Pasadena, CA) ran out of TMobile phones very quickly on launch day. But like you said, they are the same exact phone as the AT&T model, so there shouldn't be any problems with making them. I'm just waiting anxiously and checking its status every now and then. I was really hoping I would be one of the lucky ones to have theirs shipped by today but it doesn't look like that's going to happen.