I have one with the brake in 300WM, POI didn't change with brake open or closed, clean or dirty bore (until it was really dirty!) or cold or hot. I shoot the 180 grain mostly, but it shot consistently with 150s and 180s too.

I have been real happy with the way it shoots. The brake is pretty effective, but it is loud. My only complain is that I got a 300wm. A few boxes cures my itch to shoot it for a while.