Different situation. The displays on Mac notebooks are already very crisp (13" mbp a little less so but still). And that retina on the iPad 3 required a battery that was amost twice as big, and it still gets worse battery life than the iPad 2. Not a worthwhile trade off on a laptop that already has a crisp looking screen. Give me battery life.
That's why the use of effecient displays make sense, those IGZO screens said to use 10% of what current LCD's consume is the underlying reason as to why the introduction of high resolution panels is a realistic prospect.