I think Apple has the perfect lineup of products to fill many needs of many different users.
Compare the lineup of computers to cars
MBA= small 2 seater convertible. Not practical for 90% of people out there, but still a very strong market, and for the people who want it, its pretty dang cool.
Macbook= Four door sedan, fits most peoples' needs pretty well, but not perfectly, and not too flashy. A sensible choice.
MBP= A four door diesel truck with premium interior. If you can't get it done with this, you should reevaluate your goals.
Same basic principle with the desktop lineup.