I would like to simply add to all of the other great things people are saying and maybe clarify a few things. STIFFNESS - When leaning forward into these boots, you will not notice these boots as being soft, or any different from a standard boot. You WILL notice the flex design when absorbing impacts, these will allow your ankles flex forward several times further than any 4 buckle boot. 4 buckle boots aren't necessarily any harder or softer, they just bottom out after flexing forward about half a degree. Also, in terms of lateral stiffness, these are actually much stiffer than any other boot I have used, which is awesome. Edge to edge control is phenomenal.
And yes, while flex is the highlight, they are wonderful in every other way, warm, comfortable, light, awesome adjustment system... the list goes on.