ScMedic, you are entitled to your opinion, but calling my opinion "complete crap" is uh "complete crap" and just plain rude.
My gf and I looked at 3 iMacs to try to find the retina display and couldn't until we went into "Display Information" or whatever it's called on a Mac. Then we further compared and I saw a difference with my head 4 inches from the monitor, a small one, but I did see it. She never did and just went along with me. We both have perfectly fine vision. Perhaps it was the bright lights of the Apple store, maybe I would have noticed more at home (I'm sure I would), but that was what I saw, just relaying it here. A good friend of mine across the country said the same, but he also says going from his "retina equivalent tablets" to his normal computer displays, he doesn't notice a big difference. That's not saying there isn't a huge difference to some people but to me and my gf, we did not see one at the Apple Store. As they say, YMMV. I have an iPhone 4s with "retina" and I don't see a big difference in clarity vs my 7 year old IPS monitor.
There WOULD be a difference when opening say, a full resolution image, for more real-estate, but I did not do that. Unfortunately that seems to be part of the issue with LR (too many pixels),and why I went from almost pulling the trigger on a new iMac to now either waiting or building my own PC again. I'm also dismayed that a brand new ultra powered computer has issues with transparency, when my 10 year old PC that I build myself has been running transparency all decade with no issues (OS X looks very much like Windows 7 that I've had installed since it was released, full transparency, flat icons, super fast GUI). I'm only running 1080p, but it's still sad that a 10 year newer machine has issues with something as ancient as transparent windows. From what I've read, it's due to poor code in Yosemite. Opengl (or was it OpenCL) performance for GUI took a huge drop in Yosemite vs Mavericks in benchmarks. I read a bunch of this on the Apple forums. Again, sad for me because I WANT that all-in-one display.
Just as I was told when the D700 and newer cameras came out just how mind blowing the LCD screens were compared to the old ones (like my 1D3), I went to a store and had a look and noticed a small improvement, but wasn't blown away at all.
To each his own. I respect that some think there is a "night and day difference" with the new retina display. I looked hard and didn't see it. Difference? Yes! With my face up to the screen. But huge difference otherwise, no. Still a nice display for sure.