Those things are scary on the trail. I still love the K model, but from a performance perspective, they are sketchy at best (real world experience).
Straight on, or in mud, etc. they can climb about anything, and they have major funk-factor appeal to me. However, articulation is so limited and the track so narrow that they are like driving a circus ride on the trail. Gearing is not low enough either, which exaggerates the issue.
I am not saying they don't make a great overlander, as they do, but I would not recommend someone buy one for their trail prowess... Just my opinion of course.