iOS 9.3 is coming in the Spring and will introduce Night Shift as well as a number of other new features.
Tim Cook: I've Given Up Physical Keyboards, Use iPad "80% of the Time"
Cook says that he does spend time on the Mac but spends 80% of his time on the iPad. "And of course" Cook says, "I have [my iPhone] with me all the time."
Cook also shares that he gets many emails from customers and loves it because "they talk to you as if you're sitting at their kitchen table." He does share that he sometimes "gets an earful" from dissatisfied customers.