Philip Greenspun talks about using a mobile phone as a computer. He may be onto something. Since these devices have added so much functionality that is too hard to use, in their current form factor, and yet they still are not good phones perhaps we should convert them into inexpensive computer terminals!
If you are an architect and want to run a computer-aided design program, the PC is great. If you are an electrical engineer and want to design circuits, a PC is great. If you are a filmmaker and want to edit video, a PC is great. For all of these customers it would be difficult indeed to supplant the PC. For a large segment of the market, however, the PC represents confusion, misery, and wasted hours.