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.
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.