Here's a question for you: how will this look on the new Mackbook Pro with Retina Display ? The tron line is 1px wide, and on that computer's screen the one pixel is too small to see.
A retina display's claim that individual pixels are small to see means you're not supposed to be able to distinguish individual pixels in an image - so curved lines appear smooth without pixelation.
It doesn't mean that a 1 pixel-wide line is invisible, or that you won't see a single white pixel on a dark background.
From what I have heard everything is up-scaled to match the native resolution so things that are not optimized for the new displays just looks kinda bad.
Images would be this way, but fonts, gradients, vectors, etc all look fine. (Unless the app itself hasn't been updated to render those in the new density. Safari works great)
It doesn't mean that a 1 pixel-wide line is invisible, or that you won't see a single white pixel on a dark background.