Even better, the Charms Bar and toggle-trigger on the left side of the screen are both within thumbs reach, so it's easy to move through the OS while still cradling your tablet in a natural position.

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Similarly, while Apple's OS X's user interface is not just easy to use but engaging, it's just a candy shell built around the kind of tried-and-true Unix software that's powered everything from phone networks to computer science labs for a generation.

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Since the OS has you scrolling through the desktops horizontally, it's all too easy to accidentally open the tray as you scroll back and forth.

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Their latest product, Rebel, is chiefly about making it easy to do what hackers have been doing for years: make OS X work on a plain vanilla PC.

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Mozilla's fledgling Firefox OS has yet to seed out to actual consumers, but when it does an "easy and secure" payment platform should be in place.

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To reach true OS agnosticism 6Wunderkinder, however, relied on HTML5 -- which makes porting an app easy, but comes with its own drawbacks, including lackluster performance. (Just ask Mark Zuckerberg.) With the revamp, Wunderlist 2, the task management platform now has truly native apps for Android, iOS, OS X and Windows to compliment its web site.

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With OS X, Apple has a base of stable, Unix-based code, making it easy for Apple to plop down small improvements on a regular basis.

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