When it was first released, iOS was one of the most innovative and different mobile operating systems, proving that touchscreen interfaces really could work. It was a large part of the reason why the iPhone was so popular when it was first released. few years down the line and it would be fair to say that iOS hasn’t changed that much since it launched. Even the latest version, iOS 6 (available for current devices, such as the iPhone 5 and iPad 4), is more of a tweak than a brand new OS.
Source : http://www.expertreviews.co.uk/tablet-pcs/1298932/ios-7-release-date-features-apps-news-pictures