The fourth version of the beta software comes just 14 days after the third dropped on July 7, 2014. By many accounts beta 4 is much more stable and refined than previous developer builds.
One of the most visible new features is a first-party app called "Tips" that was first mentioned at WWDC but hadn't been included in any of the three previous betas. Tips' tagline is "Do more with iPad. Get new tips from Apple every week." After clicking on "Start Learning" Tips takes users through a tutorial about new iOS 8 features. In it's first incarnation there are six tips included with the app:
Quickly respond to a notification – How to reply directly inside a notification
Notify me when there's a reply – About Mail's new notification feature for important emails
Hey, Siri – About Siri's new, hands-free, voice activation feature
Send a spoken message – Messages' new audio messaging feature
Quickly manage your mail – New swipe gestures to flag, mark read, and delete messages in Mail.app
Be in the shot – Camera's new shutter timer
The Tips app is installed in iOS 8 beta 4 by default and cannot be uninstalled. Each tip can be shared as a Message, Mail, Twitter, and Facebook and you can even "like" a Tip but this appears to be the equivalent of a Photo Stream Like (as opposed to a Facebook Like).
In addition to the new Tips app, Control Center was given a substantial re-design that is more flat, consistent with the rest of iOS 8. The revised Control Center sheds the black borders previously found around the icons and turns them white when activated.
According to a MacRumors post (and a growing forum thread), iOS 8 beta 4 moved Display & Brightness settings out from under Wallpaper to its own root level setting and added options to adjust screen brightness, text size, and bold text.
Settings > Messages has a new "Keep Messages" options that allow you to specify how long you wish to keep Messages. Forever is the default and options are included for 1 year and 30 days. Clicking on the latter two options displays a warning dialog that previous messages (including those with attachments) will be deleted.
Clicking the microphone icon on the keyboard (for text-to-speech) in the Messages app now transcribes spoken text on-the-fly (streaming) as opposed to waiting until you're finished dictating to transcribe your words. iOS 8 beta 3 added voice transcription streaming to the Mail app but this is the first time it's been available in Messages.
iOS 8 beta builds are intended for developers to test their iOS apps and shouldn't be installed on production devices.
Apple is expected to release iOS 8 publicly in the fall and many expect it to arrive alongside a larger iPhone 6 in the late summer/early fall time frame.