I'd agree Leonard, resting the brisket is real important. At least and hr or so in a cooler, in foil, and maybe a towel will do (but i've had mine rest 3-4hrs before w/ no issues, wrapped good). Looks like you got the flat there too. Regarding the grain, you might want to "mark" it first, before cooking. When it's raw, cut a corner off that is against the grain. You'll see the grain runs diagonal so it's easy to spot. When you cut off the corner pre-cook, you just cut the same corner post-cook knowing it's still against the grain.
Looks great though......that WSM is gonna treat you right too!