Since iFixIt beat me to the punch in disassembling the KF, I went ahead and drop and scratch tested it -
Kindle Fire Drop Test with a video.
I was astonished. The outer glass is pretty much unbreakable and unscratchable. You can carry KF in a box full of screws and nails and it would be fine.
After a bad 6' fall the LCD did break internally, but outer glass didn't have a dent on it.
When I set out testing it, I assumed that this "20 times stronger, 30 times tougher" buzz was just marketing. Turns out - it is not.