I also just got an email saying my pre-order has shipped. 6S 64gb Space Grey, woke up early on morning of launch and pre-ordered so was probably one of the earlier pre-orders (this was when the reservation system still only had the 16gb rose gold version for the 6s).
Same as @hankmoody the UPS tracking number they provided in the e-mail doesn't work yet.
Got my shipping notice on Pre-Order
Ordered 6s 64GB Grey on the 12th.
i ordered on 16th.. a popular model the space grey 64 gb... soo im betting mine will go out next week if they have limitted stock.