I wonder why the designers decided to go with painted glass. Glass (even the hi-tech version) can be easily and homogeneously colored.
I hope I am overlooking some evident drawback linked to the dyed glass, otherwise I would be forced to admit that Apple's choice is not the best one! A paint is potentially even less scratch-resistant than glass...
Well, I figured it out: while dyed glass is surely good for the back, the color tint is not as good for the screen, unless someone wants an opaque screen...
So, Apple is right!