I have not downloaded the beta version yet. I did try the pre beta or as I like to call it the alpha version just to experience the touch oriented Metro screen with a mouse. I think you already know my opinion on that.
I do think that you made my point with you last statement.
" So I'm guessing, without having tried Windows 8 yet, that 'Desktop' users will see little difference unless they need to "Zoom" the display. "
I see this as M$ rigging it so that Metro appears to be better then the desktop. I do not have any facts to back it up but I think people use zoom more then you think. Viewing videos and pictures in full screen mode would benefit from this technology. M$ is making it clear how they feel about people using the desktop and not Metro by not making this available for desktop users.