Originally Posted by JSWolf
If it's an Apple laptop, then it doesn't actually count because a retna display does not actually use the extra pixels for more on screen. My 1600x1200 monitor on my Windows computer uses the pixels as pixels. It does not use it as an 800x600 display with pixel doubling.
For example, a New iPad get no more content on screen then an iPad.
You are right about the iPad, but wrong about the laptop. I can, if I choose, set my display to not double pixels. I actually tried it once. It makes everything crazy small, but not impossible to use. As a practical matter I will almost never use it that way because the benefits of doubled pixels far far outweigh having more stuff on the screen.
And as others point out, doubled pixels mean you can read much smaller text and see much finer detail. It's tough to go back once you're used to it.