It is as unstable as explosives come- a light breeze can set it off, and the iodine gas that is created is hazardous to breathe, When I was a kid i made a large batch (enough to make a thick layer in the bottom of a large glass beaker) I set it outside to dry. after a while when I figured it wad dry i decided to shoot it with a sling shot from a distance to set it off.... I missed but the vibration from the impact of the rock in the ground beside the beaker set it off. There was a big cloud of purple gas and the bottom of the beaker was turned to glass powder, the sides of the beaker just fell to the sides. NO shrapnel whatsoever- not an explosive to do much damage with.

For simplicity of manufacture and destructive power TATP is FAR more dangerous. A trip to the hardware store and a beauty salon is all it takes to get the ingredients. The burn speed of this stuff makes gunpowder look like an oily rag. I set off a teaspoon of the stuff when i was a kid- it was unconfined just a pile of powder.... i could feel the concussion in my chest. (NOTE I intentionally did not mention the full name of TATP- kids do NOT try to make this at home! It IS unstable and VERY dangerous, given the stuff I did as a kid I am VERY lucky to have all my fingers intact and undamaged- I know a friend from college that DID lose most the fingers on one hand 'playing' with this stuff)

This is why I am pleasantly surprised we havent seen terrorist bombings in the US- if a kid can make this stuff in bulk using a little of his allowance money you can bet terrorists can too.