Terrible, absolutely terrible. There is NO separation of context, the browser address bar becomes mangled with the text below it and you can't see clearly what you're typing. The focused surface reflects without blurring items around it (like a glass indeed).
And don't get me started on the sudden flashes of light you get just by pressing on a scrollable list. Flashes. Of light. Really that distracting and annoying!
Whoever though that glass provides for good legibility and usability needs to be fired. Steve Jobs, Johnny Ive. So much missed.