Normal people don't like today's computers. Most loathe them because they can't fully understand their absurd complexity and arcane conventions. That's why the iPad will kill today's computers, just like the latter killed computers running with punchcards and command lines.
Of course, the iPad—the actual product that millions will buy in the coming months—won't replace all computers. The entire world is not going to run just on tablets, just like the world doesn't run only on smartphones and personal computers now. But Steve Jobs' Next Big Thing is the first computer that requires no training whatsoever, one that is truly accessible and useful for everyone. Just like the iPhone changed the idea of what a phone should be without anyone truly realizing it, Apple's new computer will completely and permanently change our idea of what a computer is and how it should behave.
The perception change will be so deep that it will kill Mac OS X, Windows and Linux as we know them today. At one point during this decade, you will no longer have a billion folders and file icons floating in a virtual desktop. There will be no more baffling setup screens. No more shortcuts to work around limitations and old conventions. These frustrating barriers—built during decades of evolution—are what make normal people hate computers. These barriers have now been obliterated, first by the iPhone and now by the iPad. Everyone will be using computers similar to the iPad. Not in terms of hardware, form factor, and specs. But on its philosophy. Even the naysayers would have abandoned the Desktop Metaphor by them (in fact, some naysayers already bought theirs).