09/17/2014 08:19 EDT | Updated 06/16/2017 00:54 EDT

Apple's iOS 8: It's delivery day for new mobile operating system

It's delivery day for Apple's new mobile operating system iOS 8, with iPhone and iPad users by the millions expected to download the new product.

Apple users will find iOS 8 offers features that address long-standing complaints, but also pave the way for more streamlined use of all their other Apple devices.

"With iOS 8 comes new notifications," says CNET's Bridget Carey. "You can respond to events, reply to messages, and interact with alerts right from the lock screen and drop down menu.

"Double-tapping the home button shows your recent apps, but now it'll also have shortcuts to the people you've spoken to most recently with icons of their faces across the top of the screen, and you'll tap their face to quickly call or message them."

As well, if you have a model with a fingerprint scanner, like the new iPhone 6 or the 5s, the touch ID security system can be used by other applications.

"This is probably the biggest change to the operating system since the introduction of the App Store," says Neil Bearse, director of marketing at the Queen's School of Business in Kingston, Ont.

Bearse says the biggest overarching change iOS 8 offers "is the degree of freedom that Apple has given not just third-party developers to build more sophisticated apps, but also the ability for users to customize things like installing third-party keyboards."

"They've really addressed some of the biggest complaints that users have had about the system and also some of the biggest constraints that developers have felt in the past."

Last year's update —​ iOS 7 — was more along the lines of "let's-give-everything-a-new-coat-of-paint" and a big redesign, Bearse says.

But features introduced with iOS 8, such as continuity and Family Sharing, "are all things that you're actually going to feel day-to-day, as opposed to things just looking different like last year," Bearse says.

IOS 8 will be available for:

- IPhones from the 4S onward.

- The fifth generation of the iPod touch.

- The iPad2.

- The iPad with retina display.

- The iPad Air.

- The iPad mini and the mini with retina display.