Decided on the retina
I just made this very same decision last week. I went into the Apple store to actually compare them in person, so I would know what I was getting. I lifted both of them up to compare the weights, looked at both screens closely, opened a few apps to compare the speed, etc. I ended up deciding on the rMBP.
The screen on the pro just really was much better, it really popped out at you, and the screen on the Air was just average. When I lifted both of them up, I could hardly tell the difference in the weight, which surprised me- I thought the Air would feel much lighter, but there wasn't much of a difference.
When I opened some apps, it depended on the app as to a difference. Opening Safari/loading a web page, opening iTunes, there wasn't any difference in speed. Opening something like iMovie, though, there was a difference. 3-4 bounces of the icon before opening on the rMBP vs. 6 bounces or so on the Air. So I could tell the pro was a little bit faster in intensive apps, but not much difference in everyday apps.
But that retina screen blew me away though, you'll be really happy with that if you get it. I decided that was worth it.