Me too! Today I've got my first mac, a 2.7/16/512 retina and it is just astonishing, the screen is the biggest change since SSD introduction (and I've being running 1600x1200, 1920x1200 and 1920x1080 since ever). I've got a Samsung with no dead pixels, no bleeding, just perfect. To say something bad, the bottom is a bit loose in the left, about half a millimetre, but I suppose next time I visit a Store, I would ask them to tighten the screw a bit.
I'm using 10.8.1 in best for retina resolution and have no lag at all in the UI, only when I put a folder in the dock in list mode (Applications for example) and the list has several pages, scrolling it is really laggy, as it is my first mac don't know if that is the expected behaviour, but instead of scrolling is changing whole "pages".
Really happy, really really happy. Text is just printed on the screen!
Regards