It's only been a week since Apple released the fifth betas of iOS 11, macOS 10.13 High Sierra, watchOS 4, and tvOS 11, but the company seeded beta 6 today. We're getting closer to the GM now, which means that we'll probably see more frequent builds from Apple as it focuses more on bug fixes.
There's not a lot that's new in iOS 11 build 15A5354b, other than more fixes. Tapping the Wi-Fi button in the Control Center will now disconnect from the network and disable Wi-Fi networking, and there's a new Arabic keyboard for the Najdi dialect.
Messages in iCloud was removed in the last build, and won't be coming back until a later update, likely to be iOS 11.1. This is worth noting, because such a feature would likely be paramount to the rumored cellular Apple Watch, as you'd need such a feature to receive text messages without your phone's SIM card.
In macOS High Sierra build 17A344b, the issue is fixed that prevented volumes with High Sierra formatted in APFS (Apple File System) to be mounted as the startup disk. Still, HDD-only Macs and iMacs with 3TB Fusion drives and BootCamp aren't eligible for the new file system.
Most of the major known issues have been resolved on watchOS 4 build 15R5357b and tvOS 11 build 15J5360b. watchOS does have a new issue that has to do with SiriKit on a simulated device though.
Apple also released new betas for its apps Swift Playgrounds 2 and Classroom 2.1; however, there's no new build for its IDE, Xcode 9.