Just think of it as an extra-sharp 1440x900 resolution screen. All menubars and buttons will be the same physical size on the 2880x1800 mbp and the 1440x900 mbp. Anything that's not zoomable in an application will actually take up more screen real estate on the 2880x1800 mbp than on the 1680x1050 mbp.

I'm still using a couple of ancient 15.6" Windows laptops (the cool kids all laugh at me) because they have 1920x1080 and 1920x1200 displays -- and I'm in my fifties, finding that my arms get shorter and shorter every year (that is, creeping presbyopia -- combined with myopia -- means that I need different glasses for everything now). Apart from text-based activity (development and such), I do a considerable amount of image manipulation using Photoshop and plugins. Current-model affordable machines tend to have resolutions that are far too small for my day-to-day use, making me choose between UI elements and what I'm working on. 1600x900 is far too restrictive (and yes, I own a machine with that resolution), and I'd really like the option of taking my work with me without carting around a separate monitor (the reason I use laptops in the first place).

The new ASUS Zenbook Prime runs 1920x1080 in 13": http://www.laptopmag.com/review/laptops/asus_zenbook_prime_u...

I prefer Windows--I'm going to try this out vs. the new Macbook Pro, but I may indeed pick up the ASUS.

It will work just like the iPad. GUI elements will stay the same size, only at a much higher resolution. Old apps will "see" a 1440x900 display and just look more blurry.

The @2x.png thing is already a kind of annoying work-around. Lack of fragmentation is Apple's pridepoint, but I guess this situation is going to get worse before it gets better..

I think they're keeping the size of stuff the same, just the pixel density changes so you get a clearer image.