Friends of ours have a larger version of that GMG you bought. I was impressed by wings, burgers and baby back ribs over a long weekend. The results definitely were there, especially on a very large batch of the ribs. I wish our friend would have cooked something slower cooked or larger, like a brisket, to really see it shine.
I was very excited about this but turned off by the fan noise and its fluctuations after sitting next to it for a few hours. I would not be able to stand staying close to that unit and still be relaxed. It'd be ok if it was around the corner from the porch, but then you can't smell or see what's up!
Post back with your brisket results!
G