It's all good.  I woke up at 6, and the probe was reading 175.  I wrapped and let it go another 2 hours -- maybe a tad too long. But I just had a nice smokey breakfast.  Brisket and coffee.  Mmmmm, good.
(The brisket was 16 lbs, pre-trimmed.  I stuck the probe in a tomato from the fridge, and it registered 36*, so I figured it was working.)