They are acceptable in competition and I've seen plenty of cars use them. Of course...that doesn't mean they're good. Look at all the people who have stiffening capacitors...but thats another thread.
I had a CB in my last car and liked being able to push a button and kill power to the system. I'm planning to replace and/or use a ciruit breaker with my current system. It comes in handy. The only downside, that I'm aware of, is a rumor I heard. A guy at a stereo shop warned about breakers because they have the potential to simply 'melt' into one piece before they have a chance to break the circuit. Whereas a fuse simply splits. Something to do with the moving parts inside a CB I'm imagine. I honestly can't comment on the validity of this statement but it does kind of make sense. I'm still planning to use one in my car though so...
