Yeah, my brisket was always so so when doing a low and slow, a 12 hour cook always was a pita.
Hot and fast rocks. 5 hours or so and you end up with a great piece of meat, pork butt is even better this way too. Actually I have made ribs at 300 degrees that have been damn good too. My last cook I used at 350 and it worked just as well.
And I personally go by both the prob test and temp.