My wife's T-Mobile preorder is still MIA. All she got was a "your order is our priority, we'll notify you as soon as soon as we get an update on stock."
Just so happened to walk into the Apple Store around 7PM, waved my iPhone 6 Plus at the blue shirts and the security guards, told them I was looking only for accessories. They let me in without a hitch.vThere was a relatively large line and crowd in front of the store for iPhone reservations and onlookers.
While inside, I already assumed that there was no stock left of iPhone 6 and 6 Plus, so while checking out the leather cases, I struck up some small talk with a rep and he told me about his day and how long the lines were opening day as well as this morning and all day. He confirmed, "Yeah, we're all out of 6 Pluses. We only got single digit inventory this morning."
I asked him, "Do you get stock during the day as well?"
He responded, "Yes. But they go out as fast they come in." He was fiddling with the Point-of-Sale iPhone and happened to check inventory and said, "Hey, cool. We actually do have some 6 Pluses right now, T-Mobile... 64GB and 128GB. Did you want another one?"
My eyes lit up. I said, "Sure. Do you do carrier financing?"
"Yes, let me get a hold of a free salesperson for you."
I was out the door in 20 minutes with the last 64GB iPhone 6 Plus Space Grey for my kid. Only $100 + tax down payment, rest financed through T-Mobile EIP. My wife declined to get the remaining 64GB or 128GB iPhone 6 Pluses in Silver, as she opted to wait for the Space Grey as well. Mind you, the line remained pretty long up until the close.
Conclusion: If you're inside the store, all bets are off.