It doesn't seem to work, at least for Retina iPhones #2
I'm trying it on a MacBook Pro 15-inch w/ Hi-Res screen (128 dpi), with Firefox 24, on my own website: http://gasteroprod.com/
(the pink background is the default one on my browser, you should set it to white in your CSS)
It is wrong for the iPhone 4s which should show exactly the same thing as the previous one.
I suspect it doesn't respect the viewport meta which states: