I think that a lot of people are willing to put up with the transition to OS X because of the RDF and the iPod/iPhone halo effect, but the transition away has no such phenomenon to motivate people to use a platform long enough to get used to the differences. However, this is just a general observation.
> I have no interest in putting up with sharp bits and pointy edges in Unity or GNOME 3 or KDE 4
Meh, I find that the "sharp bits" are no more sharp than those in OS X. No platform can be perfect for any given user, since we all have different preferences. The closest you can get is with a highly-customizable tiling window manager, but anything like OS X, Windows or KDE wouldn't work like this.
> The T-series Lenovos are massive, heavy, lack Retina displays, and aren't nearly as aesthetically pleasing as the Carbon X1 is. Would never buy.
You clearly are not up-to-date on this. Have you seen the T430u? It weighs less than the rMBP 15", has discrete graphics, and has similar aesthetic stylings to the X1 Carbon. The optical drive has been omitted, for example.
> for my money, retina support is just not optional anymore
FWIW, I've found it to be half-baked when a lot of software and most websites don't support it yet. Browsing the web on a retina display is rather jarring. Moreover, when I regularly use external displays at my desk, switching back and forth would be quite jarring as well.