I have a little experience with them. Pretty much help true to the threads I read about them on here. Not a bad mountain boot but for my personal preference it didnt have as much ankle support that I look for. Maybe if I would have tightened up the laces a little more it could have corrected it but with only had two laces on the top portion of the boot...I prefer three if I'm going to be packing in and out. Also had these boots on a January deer hunt, and feet got fairly cold when sitting and glassing. To answer your original question, they have a little stiffness but not over the top, all a round pretty good boot depending what you're wanting to do with it.
On a side note I saw on another thread that you had a couple used set of 10's you may be willing to sell? Mind me asking what they are? Thank you