Here's the complete changelog, made publicly available by BGR.
Notes and Known Issues
The following issues relate to using iOS SDK 7.1 beta 2 to develop code.
Bluetooth Known Issue
32-bit apps running on a 64-bit device cannot attach to BTServer.
A compatibility behavior has been added to address an issue where some web servers would send the wrong Content-Length value for “Content-Encoding: gzip” content. Previously, NSURLConnection and NSURLSession would send a “network connection was lost” / NSURLErrorNetworkConnectionLost (-1005) error in this situation.
The compatibility behavior applies only if the Content-Length value exactly matches the expanded gzip’d content. It won’t apply for “off by 1” or similar miscounting.
Crash Logs Fixed in iOS 7.1 beta 2
Crash logs now appear in Diagnostics & Usage Data in Settings.
iCloud Known Issue
If you create a new iCloud account during setup assistant, you may encounter an error when trying to enable iCloud Keychain.
Workaround: Select Setup Keychain Later in setup assistant, then enable iCloud Keychain in Settings.
iTunes Fixed in iOS 7.1 beta 2
Loading a large iTunes Match library should no longer take an especially long time to load.
Music App Known Issue
Audiobooks fail to play.
A property, minimal-ui, has been added for the viewport meta tag key that allows minimizing the top and bottom bars on the iPhone as the page loads. While on a page using minimal-ui, tapping the top bar brings the bars back. Tapping back in the content dismisses them again.
For example, use <meta name=”viewport” content=”width=1024, minimal-ui”>.
UIKit Known Issues
If a UITextField or a UILabel that is baseline aligned with constraints has attributes that change after the constraints have been added, the layout may be incorrect. The exception to this is -setFont: on UILabel, which should work as expected.Workaround: Avoid making changes in UITextField or UILabel after adding baseline-alignment constraints. If you must make changes, you should remove the constraints and then reapply them afterward. Note that this is a performance hit, so don’t do it unless it is necessary.
The backIndicatorTransitionMask from a storyboard or a xib will not be interpreted correctly at runtime.Workaround: Set the backIndicatorTransitionMask in code.