After six beta releases, Apple has determined that iOS 11.4 is ready for public consumption.
iOS 11.4 is now available for download. You can grab it by going into Settings > General > Software Update on your iPhone, iPad, or iPod touch.
The update to iOS 11.4 includes AirPlay 2, which adds a larger buffer so that small network issues don't interrupt your audio as well as a tighter clock sync between devices, which enables multi-room audio. Apple's HomePod supports AirPlay 2, and devices from Bang & Olufsen, Bluesound, Bose, Bowers & Wilkins, Denon, Libratone, Marantz, Marshall, Naim, Pioneer and Sonos will also support the feature.
In addition to multi-room audio, Apple has confirmed that the HomePod is gaining stereo support with the update to iOS 11.4, letting you set up two HomePod speakers as a stereo pair.
Also included with iOS 11.4 is Messages in iCloud, which feature syncs your iMessages with iCloud to ensure that your messages are up-to-date on all of your Mac and iOS devices. Some unspecified bug fixes and improvements are included in iOS 11.4, too.
Apple also released watchOS 4.3.1 today. This update includes a fix for an issue that would cause the Apple Watch to sometimes get stuck at the Apple logo during startup.