While the screen on the MBA isn't a particularly good screen for its class, I never had any difficulty looking at it all day when I had one. The rMB screen is clearly crisper and clearer, and has much better color fidelity and I definitely prefer it over the MBA. But the cost is in the required battery and processor power to drive it (and in font sizes for some).
If Apple were to offer the next MBA with a "best in class" IPS display (as opposed to the current mediocre one), I might even go back to an Air for the extra horsepower and ports.