I can't say from experience, but by what I've heard:
It probably won't be as good as a specialized back country boot or even an all mountain boot for that kind of riding, but it's not like it will be impossible to do. "Oh my God I can't drop this cliff because this boot is a little bit too wide and soft." It may just take some getting used to. Some guy at my mountain skis them all over the place and I don't hear any complaints from him. But the majority of people on this site say it's absolutely terrible for all mountain riding, but I don't know how many of them have actually ridden the boot.
Keep in mind: I haven't so I could be completely wrong.