I understand why it wasn't addressed in Gruber's post, but the customer-facing points he made about online sites and how they compare to the Apple site could just as well have been extended to the retail presence of the various companies. The same design aspects which take place online are also present at the retail level.

Step into an Apple Store, and the product differentiation is clear and accessible. Step into a retailer of Windows computers (in the US), and it's just rows and rows of barely distinguishable machines. Yes, Apple does include a small display card of the basic specs near each machine, but their overall setup is one that encourages visitors to use the machines and evaluate them on-site to determine if a model is a fit. These design decisions extend to other aspects of the retail experiences, from the setting, the available staff, the sales experience, etc.

It's relatively easy to see how Apple uses vertical integration in things like its product lines and manufacturing. But they've managed to combine that with vertical design in nearly every place people interact with the company. That's hard to do but always impressive to experience.