For me, it depends what the brake is used for, I don't much care for them on big game guns, but do use them on the Varmint/PD rigs.
Now to answer the ?.
I do have the JP on my Encore 6mmAI. I really like it for when I don't have spotter to call the long range shots.
It makes for seeing bullet impact real easy. That's not saying other can't do the same, I just haven't played with enough of them to know.
I don't believe the JP is threaded on, maybe some are. I'm not sure, but mine is soldered or however they do it. Some people don't care for the looks of them. I really don't care one way or the other about cosmetics. As long as everything functions the way I expect, I'm happy.
Dave