I think implying that Linux leads to "yak-shaving" is disingenuous. I've found the standard Ubunutu and KDE distros are completely usable as is; there is no need to change anything. Just because you can fiddle all you want does not mean you have to.
Moreover, my relatively tech-unsophisticated roommate recently switched to Ubunutu; he has had no problems running the completely standard setup (I think he hasn't even changed the background).
On the other hand, on OS X, if something genuinely annoys you (like the menu-bar at the top) you would find it very difficult to fix.
What a great term! I, too, am scared of yak-shaving although I recently switched to Vim which you could argue is the mother of all yak-shaving exercises (I don't regret it though).
Right. And considering the overwhelming majority of consumers are exactly those types of people, the iPhone is a better product since it is more appropriate for most people.