I think the HDR thing is for the Iphone 5 only.
Copied from MacRumours:
A multitude of minor improvements to enhance the performance of the operating system have also been bundled into the update, such as new bounce animations in Control Center, more prominent buttons in the Music app, and a new event list view within the Calendar app. Full
release notes are as follows:
CarPlay
- iOS experience designed for the car
- Simply connect your iPhone to a CarPlay enabled vehicle
- Supports Phone, Music, Maps, Messages, and 3rd-party audio apps
- Control with Siri and the car's touchscreen, knobs, and buttons
Siri
- Manually control when Siri listens by holding down the home button while you speak and releasing it when you're done as an alternative to letting Siri automatically notice when you stop talking
- New, more natural sounding male and female voices for Mandarin Chinese, UK English, Australian English, and Japanese
iTunes Radio
- Search field above Featured Stations to easily create stations based on your favorite artist or song
- Buy albums with the tap of a button from Now Playing
- Subscribe to iTunes Match on your iPhone, iPad, or iPod touch to enjoy iTunes Radio ad-free
Calendar
- Option to display events in month view
- Country specific holidays automatically added for many countries
Accessibility
- Bold font option now includes the keyboard, calculator, and many icon glyphs
- Reduce Motion option now includes Weather, Messages, and multitasking UI animations
- New options to display button shapes, darken app colors, and reduce white point
Other
- New Camera setting to automatically enable HDR for iPhone 5s
- iCloud Keychain support in additional countries
- FaceTime call notifications are automatically cleared when you answer a call on another device
- Fixes a bug that could occasionally cause a home screen crash
- Improves Touch ID fingerprint recognition
- Improved performance for iPhone 4
- Fixes display of Mail unread badge for numbers greater than 10,000
- Continued user interface refinements
The update officially disables the evasi0n iOS 7 jailbreak, patching key kernel exploits.