I'm still learning the display. Images are pretty amazing, and sharpness, focus, and other parameters may need adjustment. It is very nice to be able to not have to scroll around.
But I agree with tillsbury; one of the things that has become apparent is that it's SO much easier to organize because of the clarity of thumbnails and icons. It's amazing that you can have so many of these in window at once, and still be able to cull, add metadata, and organize simple because you don't have to blow them up. It is a huge time saver. I can actually use icon views in the Finder now to do things with groups of photos; it used to be useless to me because they were either too small or too few.
Also, I had to adjust my ergonomics. You get closer to a retina iMac. And if you use a second monitor, it may have to be further away. That required I do some sorting out on the real desktop.
I'm not a pixel peeper, but I don't think I could spend much time on a regular monitor again. Just the text sharpness, even aside from the images.