If you want to completely separate the focusing action from everything else you do through the viewfinder, i.e. metering and composition, then BBF is the tool. You've got a static scene, or a portrait, something like that. Point the camera to center your focus point, touch the BBF button, done. Now compose, meter, adjust, shoot. The focus doesn't change like it would with a half-press. I can't imagine any use for BBF with servo or continuous AF. Most of my own shooting is action or moving subjects, where the half-press and continuous focus are vital. BBF is a useless burden with that. The whole point of BBF is not that it's "better," it's that it separates focusing from other aspects of composing. Sometimes, that's what you need. I would go out on a limb and say that most of the time, it is not.