[jlsanborn]

One advantage is that you're not relying on vacuum for brake boost. If you've got an aggressive cam that inhibits vacuum this is a plus. The other advantage is that its more compact than a big-o vacuum booster. Lots of guys squeal because it's a pain to get that valve cover off with the big-a$$ can in the way. The downside is that they're pretty touchy! I haven't experienced them in my C10 yet but even on the 1 ton when you're rolling forward, pressing on the brake while you crank the motor... when that sucker fires its like WHAM! Brakes on! I'd bet the autocrosser dudes wouldn't like them because of the loss of feel and resolution but the advantage (power) is there.