Today – 16 September – iOS 9 is going to be made available.
Usually in the UK it’s around the evening time when upgrades are possible.

Below I’ve outlined the main features of iOS 9:

  • looks more or less the same, except a new font ‘San Francisco’
  • faster and more responsive performance, improved security, smaller and easier updates and longer battery life
  • built-in apps added – News app – and improved – Maps with transport info, enhanced Notes app, Passbook becomes Wallet
  • on iPads, new multi-tasking features, including Slide Over, Split View and Picture in Picture, depending on your iPad model
  • Siri now even smarter – Siri searches wider range of topics, with better understanding of what you say
  • Proactive suggestions
  • new iCloud Drive app
  • Keyboard – featuring Easy text selection, Shortcut bar and Keyboard shortcuts
  • Metal graphics for faster scrolling, smoother animation and better performance
  • SDK improvements and enhancements

Related Links:
Apple’s iOS 9 page
iOS 9 Review – The Verge
Apple iOS 9 Review – TechRadar