I received my iPhone X earlier today, but because I didn’t add AppleCare+ to my shopping bag when the preorders opened (I wanted to be as quick as possible, and I was sleepy), today I had to buy it separately.
AppleCare+ came in handy earlier this year when I (inexplicably) bent my 12.9-inch iPad Pro and the repair’s cost ended up being €49 instead of €550. After Stephen Hackett pointed at the more expensive repair costs for the iPhone X, I was even more convinced to add the extra coverage to my new iPhone. Buying AppleCare online is surprisingly easy: you receive an email from Apple with a link, which takes you to iOS’ built-in diagnostics app that verifies your device’s eligibility with Apple’s servers. It takes a couple of minutes, after which you can continue with the checkout in Safari. I never did this myself before because I thought driving to the Apple store just to buy AppleCare was easier; it’s not. The diagnostics app has an iOS 11 large title design, too.
If you also have a new iPhone X without AppleCare, Apple has a support document that explains how you can purchase it here.