Alongside Apple's new hardware announcements, the company has released a collection of software updates for those with existing devices: iOS 9.3, Mac OS X 10.11.4, watchOS 2.2, and tvOS 9.2.
iOS 9.3 has been available as a beta for the past few months, and it includes the most changes of all the OS updates released today. The update brings a new Night Shift mode to adjust the color temperature of your display in the evenings, as well as Touch ID protection for notes, a multi-user mode for iPads in education markets, more data in the Health app, and more minor updates and bug fixes.
OS X 10.11.4 includes Live Photo viewing in the Photos and Messages apps, password support for individual notes in the Notes app, and a collection of bug fixes.
watchOS 2.2 brings support for multiple Apple Watch models, allowing users to switch between them with much greater ease. There's also an updated Maps app that's more intuitive to use and has the ability to show nearby locations.
tvOS 9.2 adds in a number of features missing from the original release, such as voice dictation through the Siri Remote, and Bluetooth keyboard support. You'll can also now group apps into folders, and iCloud Photo Libraries can now be viewed using an Apple TV.
All of these updates can be downloaded now to your devices through the usual processes. Anything that runs the previous version of these operating systems can be updated, which should include most of Apple's hardware released over the past few years.