Supposedly the new panel is IGZO, which should take less power than previously. I use a retina macbook pro as my daily driver, but I don't even care about the retina myself. I guess I do care about battery life and lightness, though.

I suppose retina is a good bullet point for them over other laptops, though, so maybe it is worth it for them for improving sales.

Correct, that's one of the screen technologies that is supposedly already in place for the new iPad Airs.

That's true and Apple probably knows that. They wouldn't add retina screen to MBA and compromise on battery life. Battery life would probably stay the same.