That's my plan, too. I have pre-ordered several times in the past, and it's the way to go for me. The only thing I hate is waiting around on delivery day, afraid to even go to the bathroom, lest they ring the doorbell and then give up and go away before I can get there to answer.
I ordered a DJI Quad Copter and waited most of the day, then took a quick shower. When I emerged on and checked my delivery status on the phone, it said Delivery Attempted, Customer Not Home. I checked the door, and sure enough, there was the note on the door saying they'd try again the next day.
One thing that has me feeling uncertain is the way that they announced the available date:
(emphasis mine)
I won't be at home on September 19, but I know where I will be. And if they START to ship them on the 19th, I'll be somewhere else the next week. I have to move around a lot, and it's a pain having to plan to stay put for the delivery truck.
When I place my order, if I get the "delivered on September 19" message (as usual), then I can plan around it. If I get "ships on September 19", then I may have to give someone else a chance to buy that iPhone, and wait until I can buy one in the store, cash and carry.