I think the biggest advantage of high heat, is that when you screw it up, you've only wasted 6 hours of your life instead of 12 hours.
Since we know it's possible to produce very tender and juicy brisket in a 350 degree oven, it makes sense that a tender brisket in a high heat smoker should be possible also. Like kickass said, the hardest part is timing. The window between undercooked and overcooked is much smaller at high heat.
