While many people put in their pre-orders for Apple's newest iPhone, what could really be the tech giant's difference maker is what comes out two days beforehand: iOS 7.

Apple will release its massively overhauled mobile operating system Wednesday for free and it will feature as many if not more changes than the iPhone 5C and 5S. During the World Wide Developers Conference, Apple CEO Tim Cook said iOS 7 would be the largest change to ever happen to the iPhone.

According to the Los Angeles Times, experts said the new operating system could end up being pivotal for Apple users. It could either drive frustrated customers away or re-excite loyalists and pull more in.

"I think people aren't anticipating how big of a deal the new iOS 7 will be," said Carl Howe, a Yankee Group analyst. "The software is very different than where they've been. And the thing that is going to blow people's mind is that it's going to make it feel like they're getting a new phone."

The software update will be available for any iPhone 4, 4S or 5 and will come stock with the 5C and 5S. Some speculated iOS 7 could slow initial sales of the new iPhones because the update will feel like receiving a new phone. Especially for users who are not eager to spend a whole lot of money to get the 5S' fingerprint reader or A7 processing chip.

For any iPhone user who is happy with their screen size and processing speed, the iOS 7 update will be like getting a new phone.

For one, the interface is getting a complete makeover from icons that appear to rise off the home screen to flat matte-colored ones. Second, users will also have access to iRadio, Apple's answer to Pandora and another update of Siri.

That is not even close to the only new features iPhone users can expect in iOS 7, reported MoneyWatch.

Now, simple setting changes are a swipe away. The new control panel appears with ease, allowing users to manage Wi-Fi, airplane mode, Bluetooth, screen brightness, the music player and more.

AirDrop goes one step further than iMessage. Using Wi-Fi and Bluetooth, iPhone users can easily share videos, photos, contacts, documents and other files without having to open an email or text message.

Multi-tasking has finally caught up to other smartphones. Now iPhones can download app updates in the background and all apps should also be able to properly run simultaneously.

Safari may make you delete Google Chromes mobile web browser. Safari will look totally different with better searching, tabbed browsing and promises a minimal web browser experience.

The camera and photos apps will also look brand new. If you have an iPhone 4S, your camera is just as good, megapixel-wise, as the 5S. However, the camera app will rework its capabilities entirely, adding filters (yes, like Instagram), better controls and a feature called burst mode that acts as a sports lens, snapping several consecutive shots in succession. Also redesigned is the photos folder, separating photos into "years," "collections" and "moments."

As for improvements to Siri... I'll believe when I see it.