The M500's user interface is fairly intuitive and it's not like we had any trouble figuring out how to get around or do stuff once we'd spent a few minutes with it.

ENGADGET: Review of Motorola's 5GB M500 MP3 player

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.

FORBES: Apple's Greatest Innovations

Finally, the company is demonstrating a concept that it thinks will be able to extend your smartphone's user interface.

ENGADGET: Neonode's Proximity multi-sensing technology hands-on (video)