I've known a number of people that tried a boom brake, only to take it off and return it. All of them, in fact. I've tried them (several brands) and find them useless.
* Must be adjusted for wind speed. Constant fooling.
* More junk under foot, more on the side deck.
* Not a substitute for proper line management.
For me, it is simpler, faster, and safer to manage the boom with the traveler and sheet. Brakes are scarce around here (<1 in 100), and I think this is the reason. When I need a preventer, I rig one.
That said, some folks really like them. From what I understand, they use them more as a quick preventer (just haul it tight) than for boom control.
You might want to borrow one first.