I was going to spurt out that argument here, but I never got around to it. See, Apple's success post-Jobs-hire has revolved around giving the customer what they really want- What's Cool.

OS X is founded on a primal awareness of two things - fashion changes on a daily basis, and the Open Source/*NIX space cranks out a lot of shit for free on a daily basis.

The iMac wasn't particularly new, different, or enduring, but Apple spared no effort in ensuring it was Cool, from the initial industrial design to the neverending product placements. If there's one thing Jobs knows, it's Brand Engineering. (Unfortunately, he did so well with NeXT- core branding: 'The computer you will sell your children for.'- that the only customers were those who really wanted/needed to look like they'd sold their children.)

Anyhow, OS X sets up an interface between You, the Customer Out There in Middle America, and the Freshmeat slaughterhouse. At first, it looked like Quartz would be the filter to determine the wheat from the chaff, but Coolness travels on Internet Time (read: Geeks laud friends for choosing OS X. Geeks tell friends about Mozilla, OpenOffice. Friends ask geeks to actually, say, *install* same. Geeks discover they really do live in Hell.), so they ship the headless X server.

Result: Middle America is pleased. They get to revel in the New Hotness even before the Windows crowd, and the Switchers have already learned to associate butt-fuggly windows with Branding. (See: AOL. WinAMP.) Consistency is not on their minds until it bites them in the ass; the experience may never be fully 'stable' (as in: nobody will be allowed off the upgrade treadmill), but that's the price you pay for the illusion that you are a Hip, Happening Mover and Shaker.

For those concerned, there will always be the boneless chicken- iApps, Safari, and so forth- which will retain brushed-metal consistency among themselves. Keeping the theme proprietary to Apple ensures that those wanting/demanding consistency will come back to the Store before throwing their money at some third party, especially one that doesn't subjugate to the standard Aqua look.

In other words, Apple's thrown off the shackles that were keeping it down through the '90s. If the system *is* consistent, reliable, and responsive, where's the upgrade motive? Make the slide to Good Enough engineering- with the faith that your engineers will be so disgruntled as to keep your Good Enough better than everyone else's- blind everyone with a blast of Fashion, and suddenly you've got a functioning business model again. If the market is growing, pretend you're at a stable milestone; if it threatens to contract, force a Buy-It-All-Over-Again event that brings in some revenue and dazzles a few more onlookers into jumping on board.

(With the apparent loss of the G5 and the wait for the 970, Apple's level of choice in triggering a true repurchasing event has been limited. The Music Store seems to have been total serendipity, and another creepy example of Jobs' associative intellect: If you can't pull a 'smash hit' out of your own sleeve on time, make a fast- and prolonged- buck reselling others'.)