Less than a week after iOS 11.3 was released to the public, iOS 11.4 beta dropped for developers on April 2, then became available for public beta testers the following day. If you're an iPhone user, there doesn't seem to be much to love about iOS 11.4 just yet, since its mostly geared toward education uses for iPads, but Messages on iCloud is back, as well as AirPlay 2.
The most notable addition to iOS 11.4 beta is the ClassKit framework for education apps, which works in conjunction with the "Schoolwork" app on iPads in schools. Obviously, anyone that doesn't have an iPad from school will miss out on all of the possibilities ClassKit provides, though, maybe one day Apple will finally open these education-only features up to everyone, most notably, Share iPad.
Aside from that, iOS 11.4 marks the return of Messages on iCloud. It was included in all of the iOS 11.3 betas but was sorely omitted from the stable iOS 11.3 release to the public. Well, now it's back, and hopefully, it won't disappear when iOS 11.4 becomes available to everyone in a few months or else we're looking at iOS 12 — a whole year after the feature's announcement.
Also back is AirPlay 2, which made a quick appearance in early iOS 11.3 betas but was quickly removed. Seems like it needs a lot more testing before it's ready for prime time. And there's also HomePod stereo pairing again, but it doesn't work right now because it needs a HomePod beta update that doesn't exist yet.
There does not appear to be a fix for the non-functioning 3D Touch issue on most iPhones, but that will hopefully be addressed in an iOS 11.3.1 update soon.
While we're still digging into the beta, there doesn't appear to be a whole lot new here for iPhones. We'll keep prying to see if there are any hidden features to name. Otherwise, those who are a developer or public beta tester with a valid configuration profile can download the latest beta right now. Jump to "General" in your Settings app, tap on "Software Update," then follow the on-screen instructions to download and install iOS 11.4 onto your iPhone.