Apple has pushed the fifth beta for iOS7 to developers as an OTA today. The latest beta brings about a redesign of control panel icons to make them more colourful along with disabling the notification centre from apps- such as games where you might accidentally pull it up.
Some additional improvements are as follows
- New Slide to Power Off
- Updated in call buttons
- Performance enhancements animation tweaks system wide (ie receiving notification will now darken instead of blur on lock screen)
- Pull down banner on push notifications
- Headset controls on headphones now working again
- Twitter and Skype now working
- Install screen and Boot screen same color as your phone now (white iPhone has black apple logo and white background)
You can follow this thread on MacRumors for a more complete log of changes and user experiences.