So in case you were wondering why Apple keeps obscene piles of cash around, that's why.
The other issue is that Apple has enough money to invest in factories, not that it owns them, but it can put money up front to encourage building them. I would not be surprised if they had a 1 year hold on screens of this size, just as they did for the iphone 4 (although even today noone is using the same screens as the 4).
Apple is probably the worst offender on that issue, in fact.
They aren't standouts (although the 15" at 1680x1050 is really nice), but they're no worse than anybody else.
EDIT: I misread the original post. Sorry about that. That said, OS X isn't appreciably worse as far as resolution independence than the rest of your options. (Not that that's praise for OS X, but neither GNOME nor Windows are particularly good either.)
Windows 7/8 "kinda" work in this regard - I have to use accessibility addons in firefox to make it play nice, IE just stretches everything, I have no experience with OSX.
You hold your laptop significantly farther from your face than an iPad, thus a lower PPI is sufficient. However, a 9.7" display with the iPad's PPI is getting close to acceptable sizes for small laptops, like the 13" MacBook Pros.
I'm still sad that even the MBP 17 comes with a 6-bit PVA panel. It's a nice panel, but dramatically inferior to an 8 or 10 bit IPS.
It all makes the IPS panels in the iPads even more impressive. From what I've read the IPS panel yield goes down with DPI, too, so the panel in the iPad (Early 2012) is amazing.
Then again, maybe those hints are only necessary because of the limitations of low resolution displays. If each pixel is barely large enough to be discerned by the naked eye, single-pixel accuracy may not matter so much. Clearly resolution independence is still desirable for accessibility reasons, even at the end of the pixel density road.
I was thinking the same thing. It's amusing to think that Apple found resolution independence harder than waiting for/making panels quadruple in size. Certainly good for marketing though :)
Its not like that part is a COTS part that is available to all OEMs.
Look at the prices of your average 47" LCD HDTV sets, way over $500. And they're probably making less money per unit than the iPad. I don't know how Apple is doing it.