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Watch out, iPhone owners: iOS 7 may sneak up on you

iPhone 5S and iPad Mini running iOS 7
iPhone 5S and iPad Mini running iOS 7.Apple

You know how your phone reminds you when an update is available? In the coming days, most iPhones and iPads sold since 2011 will alert you that they're ready for the eagerly anticipated iOS 7. While the major overhaul of the mobile operating system does improve on many aspects of the iPhone and iPad interface, it's a radical departure from what you know (and may love). This time around, you should approach the upgrade with caution, possibly even hesitation.

iOS 7 has been, in Apple's own words, "completely redesigned." Gone are the fake notebooks and green-felt gaming tables; the faux glare and shading of icons to suggest three dimensions. And it's not just a flatter, more modern look and feel that you get with the free upgrade: An upward flick of your thumb brings up an all-new Control Center, with quick access to core functions like music controls, Bluetooth, Wi-Fi, Do Not Disturb, plus the camera, calculator and a new built-in flashlight.

Notifications and app switching have both been improved dramatically, but remain more or less in the same place. More radically redesigned are the camera (now with Instagram-like filters) and photo library, which lets you zoom in and out to see what pictures you took when — and where.

You'll even find completely new features, such as AirDrop device-to-device filesharing, the iCloud keychain for keeping track of all of your passwords, and Safari's shared links, which bring everybody's socially posted links to you in one stream. There's also iTunes Radio, a Pandora-like experience that's ad-free for people who already pay for iTunes Match.

Not so bad, no? But still, you might not like it surprising you.

What could go wrong?
First of all, to the change-averse, the important thing is that this is a one-way upgrade. So even if all goes well, you may not like it. And if history is any guide, you'll have a hard time getting back to iOS 6. 

Even if you are excited about it, you shouldn't go and agree to the upgrade until you've had a chance to study it. In addition to the above video, Apple has a terrific rundown of what's new. For less slanted takes on it, have a look at pieces from our friends at Laptop and Lifehacker

iOS 7 compatibility chart
iOS 7 will run on most Apple devices sold since the beginning of 2011, with the exception of the first iPad, and all but the most recent iPods.Apple

It's important to do a few things before upgrading, as usual, such as making sure your iPhone or iPad is backed up to iTunes on your computer or up into iCloud, and that you personally know where all your photos are (don't just trust Photo Stream to have your back on that).

And as usual, you should check our site and other tech news sites to learn about upgrade woes. It's not likely that Apple will have a hard time updating all the hundreds of millions of qualified devices out there, but if there's anything really wrong, rest assured the tech press will be reporting it. It pays to be cautious, even wait a few days — the last thing you want to do is get stuck in software download hell, or have some weird activation issues. 

But you should also do another thing: Upgrade your apps. Amazon's Kindle app, for instance, needs to be upgraded before you move to iOS 7 so that you don't risk losing your local files. There may be other apps that need to have the right software coding in place prior to the update, so pay some attention to the little number on the App Store icon. (For the last time, that is — in iOS 7, apps will be able to update themselves if you allow it and those pesky update notifications will disappear.)

There's certainly a lot to like about iOS 7, but you'll like it better if you plan for it. And if you don't like what you see, don't upgrade! Remember, there's no "classic" mode in this new operating system.

Wilson Rothman is the Technology & Science editor at NBC News Digital. Catch up with him on Twitter at @wjrothman, and join our conversation on Facebook.