I am not trying to discount the elegant design and "coolness" factor of iPods by saying they have become mainstream. Perhaps the disagreement is over the definition of "mainstream" itself.
But, having spent considerable time in Manhattan (and Boston), I can tell you that you will see just as many people listening to iPods riding the subway in Manhattan as you will see "rich yuppy women" listening to their iPod minis in upscale, chic gyms.
In my opinion, when you see one out of ten people on the subway listening to an iPod --- they have become mainstrean --- and not just a plaything of the social elite. This is more than the mindless masses following the next "in" thing.
Also remember, the SOHO Apple store is one of busiest in the nation. There are also thousands of "poor" students (NYU, Columbia, etc.) and "poor" recent grads purchasing iPods.
Perhaps Apple has done something more with the iPod than create the next trend. Maybe they have produced a really great consumer electronics device --- one that people feel $299,$399,$499 is worth the price.
I do not agree with your analogy of an iPod being the same as a Mercedes or Porsche. It is a nice compliment to Jobs however.
And, if the only reason consumers purchase iPods is because they have become the "in" thing (which I only partially agree with), how is that an argument that they are NOT mainstream. I thought that as soon as something becomes the "in" thing it IS mainstream.