More than 2x actually - the guy behind the glass would be dead, unlike the one behind their improved glass. I'd say this is a significant difference - they deserve some extra credit for keeping the guy behind their armor alive.
I do find the title a little misleading though, since this has nothing to do with metallic aluminum as one would expect from reading the title.
I think what twelvechairs meant is that you have to buy (at least) twice as much of the old stuff to keep the guy alive.
If the new stuff is the same weight by volume as conventional laminated glass, then you'd have a 50% weight savings.
If the new stuff is thinner, and lighter, then it'd be useful for applications where the current glass is too thick and/or heavy.
Also, in applications like secure windows for bank tellers and such, something thinner would probably be better aesthetically. When you're dealing with someone behind a thick sheet of glass, it puts a different tone on the interaction.
Quote from the Daily Mail article linked above.
So in reality this is a modest improvement (2x) over existing laminated glass armour for use where both thickness and resistance are critical (ie. probably for specialist military applications only)