Well I think it's all about touch-screens. Decades ago they sucked. Only recently they work great. So Apple jumped in at the right time. As said (ZeroGravitas)

Well I think it's all about touch-screens. Decades ago they sucked. Only recently they work great. So Apple jumped in at the right time. As said (ZeroGravitas), people want a desktop in another form: laptops, smart-phones, handhelds, gaming devices (PSP, DS), MP3/MP4 players... Others did not fail. But Apple is very good at creating wannahaves. With the iPad they created another one. People will pay lots of money for this device because it's a hype. And that is what Apple does. Creating hypes. The iPad is nothing new. But it's got this 'look at me' factor. But try using it in the sun.... The Adam does a better job there.