Daring Fireball has a very eloquent entry on how Apple has no rival to push them to be better and give consumers more choice.
If Apple is BMW, who is the Audi pushing them to be more elegant, or the Acura or Lexus pushing them to be more reliable?
The sensibility and technical expertise that Apple brings to its product is simply unmatched in consumer technology. And while I'd love for a rival to emerge, I don't think any major tech company actually wants to play the same game as Apple. Although if one were to emerge, my money's on HP, I think Sam Lucente is doing amazing things.