Compared to the others: bad gamut (color reproduction/range). Also, even if it's better than the typical low-resolution 1366x768, it still isn't 1600x1900 or full HD. Brightness- and contrast-wise it's great. But still, there's better displays in the cheaper price range already, like on Zenbook. Or if you want to compare against much cheaper iPad, iPad also has far greater resolution, much better (almost perfect sRGB) gamut, better contrast, and so on. MBAir's display is better than average though, so it's not bad. It's just there's better options available.

Of course, if you're not interested about the color reproduction, this might not affect to you. But if you want to edit photos or see movies like they're supposed to be, then it matters.