I've done a brisket twice. The first it smoked for at least 6.5-7 hours at around 250-300 degrees. It was tender, but I made a BIG mistake and cut it wrong.
What a mistake. It was still tender, just a little tough to chew.
The second time, I dropped the temperature in the pit to 225-250 and smoked it a good 8-8.5 hours. Like the ribs, I wrapped it in foil when it started getting too charred on the outside. Cooked it to the proper internal temp, and made darn sure I cut it across the grain. It melted in the mouth. Very tender and juicy. The smoke ring was almost an inch and the crust had an amazing burst of flavor and spice. The only problem was, if you didn't get a bite of outer crust, the flavor was a little bland as well. It was only a 4 pound brisket, but very very good.