I had (have) an Air, and used it for 3 years until the motherboard died. I used to look at retina screens and wonder what the big deal was - really didn't see that dramatic a difference, sure it was a bit sharper, but the air was fine.

When the air died, I had major deadlines, and Apple wasn't going to get to repairing it for over a week, so in a bit of a panic, I bought a 13" macbook pro retina, so I could restore from backup and get right back working.

Ended up taking a couple runs at repairing the air (which actually was a wonderful experience - they replaced the main board for something like $300, and also gave me a new battery at the same time for free (was not expecting that at all).

But, when I got the air back and turned it on, after having gotten used to the retina screen, I couldn't believe how blurry and low contrast the screen on the air was. Was a huge difference.

CSB...

It only gets apparent if you directly compare it with a Retina screen. If you just use it then well, it's a screen, perfectly capable of displaying pixels. What you might notice are the viewing angles.