Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Just now, It took me 26 Seconds on the dot to purchase the Mophie wireless charger that was in my favorites added to cart and purchased with Apple Pay. Granited this was purchased on a standard day without millions of users trying to purchase the same item. Whether or not it will take my 26 sec's to complete my iPhone X preorder is up in the air.
 
Going back to 2014, my order went in 34 minutes after pre-orders opened for the iPhone 6 and I still got it on launch day. At that time, I didn’t have an iPhone, iPad or MacBook so was ordering from my laptop. Tried for half an hour and as soon as I switched to Internet Explorer instead of Chrome, it sailed through.

Fast forward two years, upgrading to the 7 Plus, I didn’t imagine I’d have any issues. 8:03 and it was available only in silver and gold.

Who knows how it’ll go, but if I had to guess, the forums will be full of screaming people unable to access the Apple Store to order and 3-4 week shipping dates within twenty minutes.
 
One thing is the 'denial of service' that inevitably happens.
This time I think it's going to be bad.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.