[Updated to add watchOS 2.2 release] At the March 21 special event, alongside the various hardware announcements, Apple also released public versions of updates for iOS and tvOS. Both new releases bring some new features along with them, but are focused primarily on small "fit and finish" issues as well as improving security, speed, and
fixing bugs. One feature shared between the new iOS 9.3 and the forthcoming OS X 10.11.4 is the new ability to create and encrypt individual notes in the Notes app using a passcode and Touch ID.
The iOS 9.3 release will also feature a new Control Center button, called Night Shift. The program, which can be turned on or off, uses color-shifting to gradually turn down the amount of blue light emitted by the display hardware after sunset. Research has show that this can reduce eye fatigue, and may also contribute to better sleep quality if users are using their devices shortly before bedtime. Scientists currently believe that computer activity shortly before going to sleep hinders getting into the sleep state, and lowers the quality of the sleep.
Also improved is the 3D Touch feature, now augmented with more Quick Actions. In addition, the navigation capabilities of the Apple Pencil on the iPad Pro -- a feature removed during the early betas for iOS 9.3 -- were returned, with improvements. When using the forthcoming watchOS 2.2 update, users on iOS 9.3 will be able to pair multiple Apple Watches to a single device. Also, third-party apps can now add songs to Apple Music.
There are other improvements for iBooks on iOS (now able to support PDFs through iCloud), CarPlay (new Maps and Apple Music features), Apple News (a landscape view and support for embedded videos, faster updates, personalized recommendations, and other improvements), and Verizon customers will see support for Wi-Fi calling. In addition, there is also a new educational enhancement for teachers and administrators using iPads and iTunes U in classrooms, and the Health app will include a new "Activity Rings" view based on the design seen on the Apple Watch.
Also fully fixed in this release was a security hole that had been
partially patched earlier that could conceivably lead to brute-force attacks that might decrypt iMessage contents, ironically among the sorts of access the FBI wants Apple to provide. The existence of the flaw, which would be difficult to duplicate "in the wild," nonetheless strengthens Apple's argument that it is in a constant "race" against hackers to harden, not weaken, its security -- because even just proof of any flaw could lead to it being exploited widely beyond the narrow confines of government-security or law-enforcement requests.
The tvOS 9.2 update brings a few new features to the operating system, including support for home-screen folders, a redesigned app switcher, restored support for Bluetooth keyboards, and more. Also included is voice dictation through the Siri remote, which will vastly speed up searches for specific titles or apps. MapKit compatibility has been added for developers to use in apps, bringing Apple Map geographic or navigation information to the Apple TV and third-party apps. Support for the iCloud Photo Library has also been added.
Folder creation on a fourth-generation Apple TV
Update: Following the public event, Apple also released watchOS 2.2, which supports the aforementioned tying of multiple Apple Watches to a single iPhone if desired. It also offers an all-new Apple Maps view and Glance, along with enhanced information from Yelp, and the ability to set destination targets like "work" or "home" that can be instantly navigated to. Users wishing to update their Apple Watch to the new release must have already updated their iOS device to today's v9.3 release.