I tend to agree with you that partitioning the market into two tiers ("junk" and "premium" in particular) is an artificial distinction but I disagree with your

I tend to agree with you that partitioning the market into two tiers ("junk" and "premium" in particular) is an artificial distinction but I disagree with your characterization of the iPad mini as something from the bottom tier. It is a different form factor, but that isn't the same thing as lower quality or less featureful. Apple isn't afraid to use form factors, feature sets, and multiple SKUs to partition the market it is just that they focus on partitioning the upper-end of the market and not the entire market. I wonder if Apple could ever manage multiple brands to partition the market even further in the way that Gap Inc, partitions the clothing retail market via its Banana Republic, Gap, and Old Navy brands.