The newest version of the Zap&Go still claims 5 minute charge. The old (cylindrical) one claimed 1.5Ah. The new one looks bigger. In the details on their web site there is a claim to having tested it at European 230V 40A (I don't know many outlets that can deliver that current, most are limited to 10A, some to 16A and the older ones can be as little as 5A). 40A is not kosher!
So, 40A for 5 minutes gets you 3.3 Ah. Assume 100% efficiency in all directions and that gets you about 4000F at 5.5V, or 8000F per cell.
Maxwell make 2.7V 3000F cells that are 0.5kg. So that's about 6 cells or 3kg. Big Beastie!
More likely they are still getting the 1.5Ah, so that's about right, being 5 minutes at 16A and requiring 2x3000F cells, or about 1kg.
As many have pointed out, the really exciting bit is their transformer, which they have claimed is exciting and patented.
The graphene bit is a bullshit. There may be graphene in there, but there are no graphene supercapacitors that have more energy than ordinary activated carbon supercapacitors. Their MSDS claims graphene-carbon composite (and ioic liquid electrolyte). I suspect they've just sprinkled a bit of graphene in to be able to tell the truth that it has graphene in it.
So the device probably works as described. But who cares? 1500mAh is nothing. My phone has a 3Ah battery, let alone a iPad or other tablet at >7Ah.
There are Li-ion batteries that can charge at up to 100C, easily 10C. Why make a supercapacitor?