Noise and "backblast" to the shooter aren't bad, but as with any brake it isn't kind to anyone shooting beside you. My spotter can position himself behind and to the side of me, and isn't effected by the muzzle blast.
I have an FTE brake as well, and I don't notice any significant difference between the two for recoil dampening or "backblast". I can't really comment on which is louder or quieter as I always wear hearing protection and thus both are adequately blunted.
My gunsmith recommended this one instead of a FTE because he suggested that it may effect barrel harmonics, but I can't say that I've rigorously tested his theory.
HMMMMMMMMM. WELL, CRAP. Im having ideas now. Trim the bbl. to 23'' and install an mrad brake. Cuz I havent shot prone with it for long periods but it definately whacks the top of the shoulder. 300 Win Mag is fun but it kicks, even on a 17lb rifle like mine. Prone is the only thing that starts to get me but I like shooting prone the best. Thanks for the info.